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1. It clears the contents of all text boxes sets the check box to unchecked and clears the authorities list Integrating the data access layer If you run the application now and try to find and save users you will get messages telling you that you have saved users successfully and messages that none of the users you have saved can be found This is because the find and save methods of UserServiceImpl are yet to be implemented The required implementation is described in my Data Access Layer Design for Java Enterprise Applications article and can be downloaded here 9 First drop the classes and interfaces from the data access layer into a newly created uk co marauder usermanager dao package The required classes and interfaces are E AbstractDMRegistry E DMRegistry E HibernateTemplateDMRegistry private void saveUser final User user userService save user new AsyncCallback lt Void gt Override public void onFailure Throwable caught Window alert caught getMessage Override public void onSuccess Void result clear Window alert Saved user getUsername successfully oe E UserDataMapper UserHibernateDataMapper UserManager not to be confused with the client side UserManager You will also need the Hibernate JAR and the JARs on which it depends Put these in WEB INF 1ib in the war directory and add them to the User Manager project The User hbm xml1 file is also
2. The magazine of the ACCU WWww accu org Volume 22 Issue 1 March 2010 3 2 re nat of Features PR hy Continuous Integration i One Jez Higgins Live to Love to Learn Pete Goodiliffe Assert Yourself Richard Harris Of Lag Throughput and Jitter Alan Lenton Developing Web Applications with the Google Web Toolkit Paul Grenyer Code AQUA b in C Nash cvu Volume 22 Issue 1 March 2010 ISSN 1394 3164 WWW accu org Steve Love cvu accu org Jez Higgins jez jezuk co uk Contributors lan Bruntlett Pete Goodliffe Paul Grenyer Richard Harris Jex Higgins Alan Lenton Phil Nash Roger Orr Terje Slet DELES OEI Jez Higgins chair accu org Alan Bellingham secretary accu org ACCU Membership Mick Brooks accumembership accu org ACCU Treasurer Stewart Brodie treasurer accu org Advertising Seb Rose ads accu org Cover Art Pete Goodliffe Repro Print Parchment Oxford Ltd Distribution Able Types Oxford Ltd Design Pete Goodliffe accu cvu Some conventions allow us to operate almost automatically Doors without handles are pushed Doors with handles that do not pull often cause a moment of confusion Having to go against our familiar conventions also gives us pause Having to drive on the right hand side of the road when you are accustomed to driving on the left means you have to concentrate a bit more and pay attention to the implied things like going counter clockw
3. What do you have to contribute 12 evu MAR 2010 m What are you doing right now m What technology are you using m What did you just explain to someone m What techniques and idioms are you using LongishMethodName int firstParameter const std string amp secondPar const std vector amp thirdPara Widget fourthParameter And we haven t even added namespaces yet except for std I think you ll agree that this is a big readability issue The issue is made worse by a lack of consistency which often accompanies such attempts Sometimes multiple parameters are on one line sometimes split across several Sometimes aligned sometimes not Even if the developer is following other conventions consistently this one seems to slip through the cracks probably because it is often not defined and it can be difficult to know exactly what to do in a consistent way I have a theory about this state of affairs It s an important theory even if it turns out not to hold in this case because it touches on a principle of why people get so religious about code formatting in the first place I m going to expand on that a bit later but for now the theory is this Developers can t find a consistent style because the most obvious consistent style seems somehow wrong The underlying principle which I ll come back to is Regardless of what is objectively good what is familiar always wins out So wh
4. map find key if it map end return backmap erase it gt second first map erase it no op if called for non existing key void erase2 const KEY2 amp key2 const tBackMapIter it backmap find key2 1if it backmap end return map erase it gt second backmap erase it void clear map clear backmap clear typedef typename tMap size type size type size type size const return map size Listing B typedef std map lt KEY2 tMapIter gt tBackMap typedef typename tBackMap const iterator tBackMapIter tMap map main holder of value auxillary info is the second key tBackMap backmap links the other key to the main holder public overwrites any existing association on cvu either key void insert const KEY amp key const KEY2 amp key2 const VALUE amp value const tBackMapIter it2 backmap find key2 1f it2 backmap end map erase it2 gt second typename tMap iterator itl map find key if itl backmap erase it1 gt second first itl gt second std make pair key2 value map end else itl map insert std make pair key std make pair key2 value first backmap key2 itl throws if called for non existing key const VALUE amp atl const KEY amp key const tMapIter it map find key if it map end throw std out of range no
5. Dozer http dozer sourceforge net 10 Eclipse http www eclipse org 11 Google Web Toolkit Download http code google com eclipse docs download html 12 Google Plugin for Eclipse 3 5 Galileo Installation Instructions http code google com eclipse docs install eclipse 3 5 html MAR 2010 evu 25 4cvu lan Bruntlett discovers more nix shell tools ere are some more titbits of information about using the Linux command line prompt in Linux parlance a shell bash As a technicality I d like to point out that bash is just another program and can be replaced with a different program also acting as a shell I wrote 1 and 2 while learning about bash This short article is intended to further inform the reader building on the previous articles I am trying to balance this text hopefully being thorough without stating the obvious Note I use nix as an abbreviation of Unix GNU Linux Even DOS had pipelining where the output of one program eg grep could be piped to the input of another program e g more grep c more This invokes grep passes it the parameter c and sends the resulting output to a temporary file When grep has finished more is executed with the temporary file sent to the input of more which lists the output in pages on the screen This idea was borrowed from Unix However the implementation wasn t complete In DOS grep would be started its output saved in a tem
6. O X Xe Oe x x o xX X O X O X O ayi X O ay X O olxl o We can thusly construct a game of tic tac toe for any first choice of card and as any child might tell you this game cannot be won by either player barring error As such I should have advised Sir R to have declined to play m while first last const size t dist distance x firsttt if dist lt best best dist return best std pair lt size t size t gt score const std vector lt position gt amp first const std vector lt position gt amp second std pair lt size t size t gt score 0 0 for size_t rank 0 rank 8 rank for size_t file 0 file 8 file const position x rank file const size t first best shortest x first const size_t second best shortest x second if first best lt second best score first if second best lt first best score second return score cvu Assert Yourself Richard Harris finds new respect for the humble assert hen I started out as a for want of a better description professional programmer I was advised by a senior colleague to avoid asserts and rely instead upon proper error handling The reasoning was sound enough since asserts compile to nothing during a release build any errors that they check for will pass by unnoticed Relatively recently I came to the conclusion that this argument misses a crucial point asserts are not for check
7. it is a huge topic and well worth investigating more if you are interested This can be at best embarrassing and Personality type affects learning style If you favour the right brain mode of thinking you will learn best when presented with patterns and an holistic view of a subject rather than a serial stream of information You ll prefer to make associations and understand overarching themes If you favour the left brain you want a linear rational presentation of the topic You ll prefer to assimilate facts than to have a grand story told you Clearly your brain wiring has a radical effect on the most effective style of learning for you There are many models of personality type perhaps the most famous being the Myers Briggs Type Indicator MBTI 3 MBTI classifies your personality along four axes Your personality type will effect how you associate knowledge and how you best learn One MBTI axis 1s Introvert Extrovert Introverts would rather learn on their own they need private mental space to work things through Extroverts learn well in groups where they can discuss and feed off the ideas of others Another interesting axis is Sensing Intuition The Sensing personality is the classic left brainer who emphasises facts and details They must complete one task before moving on Intuitive people are right brainers who use their imagination more They can move on without completing a task or before they understand everything about
8. otherwise we d all be writing assembler Of course high level languages are not only about human readability They are also about portability and economy of expression among other things Nonetheless human readability is certainly a large part of it So if we use high level languages in order to make our code more readable should the layout of that code be irrelevant Looked at from this perspective we may say it should be relevant but code is also for other humans and it s the differences in styles that create the problems it all balances out to zero In the context of software development is it worth fighting religious war over a zero sum game What if there was a way to come to a consensus Would there now be some advantage to looking at layout If so how much advantage These are questions that I hope to answer shortly In the meantime here s another cliche code formatting is just personal preference It has no intrinsic value Again is it worth fighting over something that has no value But what if it did Sometimes it can be useful to look at the extremes Consider listing 1 It s not too difficult spot the familiar first c program example even if it s in a less familiar layout But are you sure it s correct It shouldn t take too long to spot the bug and even if you don t the compiler will point it out to you but now look at the same code expanded to a more canonical form in list
9. He now has the skills and experience to innovate Heed this model Don t try to transcend and innovate until you have completed the Shu phase of your learning remember to be aware of unconscious incompetence and have completed the Ha phase of understanding the knowledge These are key factors in working out how to learn most effectively Let s review them again m Learning is a basic human skill We can all do it We do it all the time MAR 2010 evu 5 Hunting the Snark 6 Of Lag Throughput and Jitter Alan Lenton gives a glossary of terms ver the last few years quite a number of people have asked me to explain the difference between latency throughput and jitter I was surprised at how many of them were programmers lt cough err software engineers gt but thinking things through about that s probably not surprising because most programmers don t usually end up at the sharp end of networking So here for your edification is the Alan Lenton guide to latency throughput and as a special bonus jitter Perhaps the best way to explain it is using an analogy Suppose we have a wedding party The bride and groom have exchanged their vows the photographs have been taken and it s time to travel to the reception There are 24 limos to take the party to the reception Everyone gets in The cars line up behind the happy couple s car and it s time to move off Now as it happens there is a single lan
10. Treasurer Membership Secretary and Web Editor and by the journal editors currently Steve and Ric I m hugely grateful for their time and their quiet efficiency over the past several years ACCU s big event the Conference doesn t appear out of nowhere of course When I took over from Ewan as ACCU Chair we formalised the position of Conference Chair Ewan and now Giovanni together with their Conference committees have worked long and hard to continue the tradition of formidably good programmes This year s programme 1s once again ridiculously good including keynotes by Jeff Sutherland James Bach Dan North and Russel Winder I m also excited that Robert Martin is coming back Uncle Bob gave me a hug last year and it was great The AGM is of course held during the Conference My understanding is that the conference was originally created to give people something else to do while attending the AGM As a means of bringing a large chunk of the membership together in one place you have to say it s proved wildly succesful You don t have to attend the Conference to attend the AGM though so do please come along if you can While the administrative functions of the organisation are important getting together with your fellow members putting faces to names making and renewing friendships is even more so Advertise in C Vu amp Overload 807 of readers make purchasing decisions or recommend products for their o
11. Windows By Jason Venner published by Apress ISBN 978 1 4302 1942 2 For a start I have to say this book didn t exactly inspire me to rush out and play with Hadoop Then there is the real problem For all that it came out in 2009 the book is based on Cloudera s 0 18 3 version of Hadoop while the The following bookshops actively support ACCU offering a post free service to UK members if you ever have a problem with this please let me know I can only act on problems that you tell me about We hope that you will give preference to them Ifa bookshop in your area is willing to display ACCU publicity material or otherwise support ACCU please let us know so they can be added to the list Holborn Books Ltd 020 7831 0022 www holbornbooks co uk Blackwell s Bookshop Oxford 01865 792792 blackwells extra blackwell co uk current version is 0 20 1 As I understand it there are radical changes to the API in the 0 20 x versions And the final killer for me at least was the fact that a substantial number of pages throughout the book are devoted to regurgitating code tables of machine settings copies of initialisations files and masses of extracts from output and log files It even has pictures of test output in Eclipse I was left with the feeling that the author had a much slimmer volume in mind but was forced to bulk it out to a set number of pages with a vast amount of mono spaced font mater
12. Zone Reports and membership news SUBMISSION DATES FEATURES Live to Love to Learn Part 2 Pete Goodliffe continues his journey of self improvement 6 Oflag Throughput and Jitter Alan Lenton gives a glossary of terms 8 Continuous Integration for One Jez Higgins sees value in team tools for one person 10 Code Formatting in C Phil Nash explains why formatting counts 13 AGame of Stategy Baron Muncharris sets us another challenge 14 Ona Game of Skill The Baron s student acquaintance plays the game 15 Assert Yourselt Richard Harris finds new respect for the humble assert 16 Developing Web Applications with the Google Web Toolkit Paul Grenyer explores web UI development in Java 26 More About Bash lan Bruntlett discovers more nix shell tools WRITE FOR C WU C Wu 22 2 C Vu 22 3 15t April 2010 15t June 2010 Both C Vu and Overload rely on articles submitted by you the readers We need articles at all levels of software development experience What are you working on right now Let us know Overload 97 15t May 2010 Send articles to cvu accu org The friendly magazine production Overload 98 15t July 2010 ADVERTISE WITH US The ACCU magazines represent an effective targeted advertising channel 80 of our readers make purchasing decisions or recommend products for their organisations To advertise in the pages of C Vu or Overload contact the advertising officer at ads accu o
13. able to use all the classes in it The easiest way to get around this problem is to copy the User object returned by Hibernate into a fresh User object that uses an ArrayList lt String gt rather than a PersistentBag This could be done manually using a copy constructor but that would get tedious as domain objects get more complex Helpfully there is a library The Google Web Toolkitis a far more powerful and elegant tool for creating List interface Unlike Java which does not WER application front ends than any of the JSP based libraries used by most called Dozer 9 that recursively copies data from one object to another The Dozer JAR can be downloaded from the Dozer website and should be placed in the WEB INF 1lib directory along with its dependant JARs commons beanutils and commons lang and added to the User Manager project Dozer s use is very simple Just create a DozerBeanMapper and call the map method with the object to copy and the type of the object to copy it to and the copy is returned The only draw back is that unlike Hibernate Dozer can only use public accessors This is why all the set methods of the User class as well as the get methods must be public Override public User find String username User user getUserMgr load username if user null user new DozerBeanMapper map user User class return user If the object to copy is nul1 map throws an exception therefor
14. all which is again one of the best books I ve read these books are great in different ways and it would certainly be a pleasure to read it again Moreover a while ago I bought Christopher Alexander s Magnum Opus The Nature of Order four books which I haven t even started reading and which would have been perfect for a desert island stranding Yet my non novel book quota is already full and this is not even one book so I d reluctantly leave these behind Regarding architecture and buildings How Buildings Learn by Steward Brand is another book I ve appreciated but it s rather more limited in MAR 2010 cvu 33 cvu The latest roundup of book reviews If you want to review a book your first port of call should be the members section of the ACCU website which contains a list of all of the books currently available If there is something that you want to review but can t find on there just ask It is possible that we can get hold of it After you ve made your choice email me and if the book checks out on my database you can have it will instruct you from there Remember though if the book review is such a stinker as to be awarded the most un glamourous not recommended rating you are entitled to another book completely free must thank Blackwells and Computer Bookshop for their continued support in providing us with books Jez Higgins jez jezuk co uk Desert islan
15. been many years since I ve read this one and I d really appreciate getting into it again so that one s in despite the rather tough limit of four non novel books Some runners up include Generative Programming by Krzysztof Czarnecki and Ulrich W Eisenecker This is a rather heavy book and it addresses quite a bit of the same issues as Coplien s book and unlike Coplien s book having read it once I don t really feel like reading it again at least not this time Another great book is The Cluetrain Manifesto by Rick Levine Christopher Locke Doc Searls and David Weinberger This is one of the best books I ve read which tells the important story of what is really happening in our networked world devoid of any hype If it hadn t been for that I ve read it twice so I know it almost by heart and due to the limit of five books it would have been included The authors are not hippies removed from reality These are hard core business people having had positions like VP of marketing at major companies One of my favourite quotes is We re immune to advertising Just forget it These people tell it like it is and reading the book gave me a similar experience as when I read Kent Beck s Extreme Programming Explained in 2001 Finally someone who tells it like it 1s For a similar reason having read a lot of agile and lean books since then agile lean books are not on my l
16. createChangeEvent this marauder usermanager client widgets It is a sub package of uk co marauder usermanager client so will be compiled by the GWT compiler In the new package create a class called ListBox Listing 8 One of the great things about Java is package scoping which allows us to create a class called ListBox which inherits from another class also called ListBox in another package As you can see in the overridden insertItem and removeItem methods the first thing that happens is the original super class method is called This is so that the insertion and removal behaviour is unchanged Then the fireNativeEvent static method of the ChangeEvent class is used to fire a change event which in turn causes the change handlers to be invoked To use the modified list box simply replace the import of com google gwt user client ui ListBox in UserManager java with uk co marauder usermanager client widgets ListBox If you run the application now it will behave as expected From a user interface point of view all that is left to do is implement the Find and Save buttons For these create another setup method called something like setupButtons and two more click handlers Listing 9 Call setupButtons right after setupAuthWidgets The Find button click handler simply gets the user name from the user name text box and passes it to the findUser method which we have not written yet The Save button click handler creates a new User
17. enabledChkBox and the authorities widgets on the final two rows grid setWidget 3 0 new Label Authorities j grid setWidget 3 1 authListBox grid setWidget 3 2 removeAuthBtn grid setWidget 4 1 authTextBox grid setWidget 4 2 addAuthBtn 20 cvu MAR 2010 amp User Manager Mozilla Firefox cx File Edit View History Bookmarks Yahoo Tools Help y A ig http localhost 8888 UserManager html gwt codesvr 192 168 106 1 9997 die Live Sea ch P A Most Visited Getting Started a Latest Headlines User Manager Username Find a Password E Enabled Authorites Done Place all of this code in the buildGrid method directly after the Grid instantiation Then to display the grid it needs to be added to the host page public void onModuleLoad RootPanel get gridContainer add buildGrid If you run the application now you will see the not especially sexy interface Figure 5 I will take a look at how to sex it up once the rest of the functionality is in place As it stands you can type in the text boxes click the check box and press the buttons but they do not do anything Next let s look at the authorities widgets The authorities list box currently looks like a combo box To make it behave as a list box it needs to be told to display more than one item The add button should only be enabled when there is text in the authorities text box and
18. g com example myproject uk co marauder usermanager Location Create new project in workspace D Create new project in C Users Paul Documents Sandbox EclipseWorkspace3 UserMan Browse Google SDKs vV Use Google Web Toolkit Use default SDK GWT 2 0 0 Configure SDKs Use specific SDK GWT 2 0 0 Ca R S E A Use default SDK none Configure SDKs Use specific SDK 5 Web Application Starter Project Mozilla Firefox File Edit View History Bookmarks Yahoo Tools Help gt C 4 http localhost 8888 UserManager html gwt codesvr 192 168 106 1 9997 5 Live Search P 2 Most Visited Getting Started Latest Headlines Web Application Starter Project Please enter your name Send Done Remote Procedure Call RPC The server returns some information which is displayed in a dialog box see Figure 3 Although this seems very Remote Procedure Call Sending name to the server GWT User Server replies Hello GWT User am running jetty 6 1_x It looks like you are using Mozilla 5 0 Windows U Windows NT 6 0 en GB mv 1 9 0 15 Gecko 2009101601 Firefox 3 0 15 NET CLR 3 5 30729 lt xml version 1 0 encoding UTF 8 gt lt module rename to usermanager gt lt inherits name com google gwt user User gt lt inherits name com google gwt user theme standard Standard gt lt entry point class uk co marauder usermanager client Use
19. it is it is hardly a constructor m In the other ctor the expression is probably correct but only due to wild chance As operator precedence is a royal mess in C expressions shall use s like r lt lt 16 g lt lt 8 b m The most accepted approach to stuff using bit operations is to use unsigned types not signed ones So d use unsigned int instead of int for the member and the operator m The second ctor would provide wild results if passed values not in 0 255 range so some checks or an assert would be a benefit On to twoway_ map The first thing to inspect is how the state is stored We see two maps one holding the first key and the value and another that has the second key and a pointer to the value In member functions we see iteration over the whole maps in a search This makes the choice a suspect With maps couldn t we do the job just through lookups And using pointers imposes fragility It is not an error in itself but drags in the obligation to be extremely careful about the pointed thing s lifetime and cross consistency The first function insert looks simple And it does what is likely intended for empty maps or new keys creating an entry in the main holder and a referring one in the other A pointer to an element in map1 is stored so we ll have to review any erase operations to remove all the referring pointers If the passed key1 key2 argument already exists in the map multiple pointers can
20. manipulate my triangles from which I might derive a system of rules for manipulating my arrays of indices Indeed I have upon my desk a number of models built out of toothpicks and ticky tack And it is here that asserts have come to my rescue By using asserts to test things that I believe to be true I have been able to discover when I have held erroneous beliefs due to my pedestrian two dimensionalism They have proven to be a supremely effective tool for whittling away at my assumptions and revealing the true rules for the geometric manipulation of multidimensional triangles I am convinced that this can be exploited in the development of any algorithm Unit tests can tell us that our code fails to meet requirements but not why With appropriate use of asserts we can reveal the why and that is the reason behind my new found respect for this humble and unfairly overlooked device W Richard Harris has been a professional programmer since 1996 He has a background in Artificial Intelligence and numerical computing and is currently employed writing software for financial regulation MAR 2010 cvu 15 4cvu Google Web Toolkit Paul Grenyer explores Web UI development in Java enterprise web applications It separates the user interface view from the application logic controller and data domain Traditionally the view is implemented using Java Server Pages JSP and there are a number of frameworks such as Struts 2
21. of such a style In this simple example we have seven points at which whitespace must be maintained for alignment purposes A compromise is to use just two columns as in listing 5 This still allows the identifier names to be easily scanned but at some loss of clarity with respect to the initialised values Arguably the identifier names are the most important element here from the perspective of fast lookup and are the most obfuscated in the original example so this is still MAR 2010 evu 11 4cvu void NamespaceQualifier SomeDescriptiveClassName a big improvement How big We re getting to that At this point I just wanted to present some options and examples with a little rationale We ll build on these shortly Blocks of variable declarations are common but spreading them out through a function is perhaps even more common making the above examples less relevant However there are a couple of places where we do still regularly see groups of related variable declarations in once place One is in class definitions where member variables are usually grouped in one place Immediate readability of the names is probably even more important here as we tend to flip back to a class definition in a header file in the case of C just for a moment to get the names But the other place and where I d like to focus further is function parameter lists Parameter lists are obviously important They define the i
22. perhaps even more surprising 1s that I d like to bring her next album Another Day as my second choice Lene Marlin has a delightful intimate voice which goes straight to your heart I d have liked to have brought all three of her first albums but I know Paul won t allow it That s it My five books and two albums Now it s just a matter of preparing to get stranded P S This time the prolonged dispute about what s the best Pink Floyd album was not continued A few books on complexity self organisation and emergence which may well turn out to be some of the most important sciences of the 21st century would also be very desirable but my quota is full and I d already have plenty to study and contemplate References 1 http Wwww cpp next com Next issue Pete Goodliffe cvu for flexibility or longevity To quote the book That which is cheap and effective is more useful that that which is big and expensive This book states that you should always store data in text files and that programs should act as filters with well defined interfaces There are a lot of pre written Linux Unix commands that are filters take an input stream stdin process filter text and send it to an output stream stdout Lots of applications can be written as shell scripts processing data that is text based far cheaper than a conventional monolithic program The pre existing commands mean that bec
23. refer to the same node in map1 or some nodes may be not referred any longer We can t tell whether it is a bug or a feature The size function returns size of the first map To me that would imply the author thought the two maps will have the same element count It is clearly not enforced in any way with proper calls to just the insert function alone we can create more or less entries in either map So the meaning of the return value is moot The assessor functions are non const and return non const reference that may work like map s operator Though this class has the state in two maps and the functions show no attempt to keep them in synch I d bet this is a serious overlook on the creator s part who did not consider here the map s feature of auto inserting nodes Possibly they even started out as const functions and const got removed due to a compiler error A correct implementation should use find and handle the not found case some way As it stands at1 would create a default initialized value to be returned while at2 would dereference a null pointer invoking problems The erase members are the most interesting beasts with all kind of problems One already mentioned earlier erase happens on the actual iterator that has a in the for Any code that walks a map and many like collections shall have the bare it only on the else branch Usually map erase it is seen on the other here it gt first is calle
24. required so that Hibernate knows how to persist the User object Put the file in the uk co marauder usermanager model package alongside the User java file The Hibernate SessionFactory which we will see how to create in a minute also requires the hibernate properties file Put it in the src folder at the root package level The data access layer UserManager class will handle the persisting and retrieving of User objects It is used by both the find and save methods of the UserServiceImpl1 class but unlike the SessionFactory class is not thread safe so a SessionFactory object should be created in the constructor and stored as a field and the UserManager created on demand Listing 13 After creating the UserManager object finding and saving User objects is trivial Listing 14 All that is required to find a user is to pass the user name to the load method of the UserManager and return the User object null is public class UserServiceImpl extends RemoteServiceServlet implements UserService final SessionFactory sessions public UserServiceImp1 sessions new Configuration addClass User class buildSessionFactory private UserManager getUserMgr final HibernateTemplate hibernateTemplate new HibernateTemplate sessions return new UserManager new HibernateTemplateDMRegistry hibernateTemplate MAR 2010 evu 23 4cvu public class UserServiceImpl extends RemoteServiceServlet impleme
25. string txt2 world std vector lt std string gt v char txt hello int 1 1 std string txt2 world std vector lt std string gt v char txt hello int i 7 txt2 world std vector lt std string gt v std string another eye brain insight that I ve not mentioned yet Briefly reading speeds can be enhanced by the use of a guide This may be a moving object such as a finger or pencil but just having a hard edge can be helpful too However too much of the same thing can make it harder to keep track of where we are so if the hard edge is too long it loses some of its effectiveness It follows therefore that small blocks with hard edges achieved through alignment should help the eye to more readily distinguish the associations between sections of code A lot of these are things we already do to some extent Our use of code blocks and indentation help visually organise code to make it easier to take in but can we take it further One good example is blocks of variable declarations I ll be using C as an example here as that has been my focus in this but most of what I m talking about applies to most if not all programming languages I d argue that you ll notice the difference in C more than most So here is a typical stretch of variable declarations in listing 3 Already this is organised into a little island If the declarations were scattered around we would lose
26. that can help you do this However fundamentally you still have to write JSPs and they are cumbersome and difficult to test T he Model View Controller pattern 1 is often used to build Java based Writing a user interface for a Java application using JSP does not make much sense when you consider that the rest of the application is written in Java If there is any functionality shared by the user interface and the application logic it must be implemented and maintained twice If you have objects in the domain that need to have all or part of their state displayed you have to decompose them and transfer the data to a page to be displayed The Google Web Toolkit 3 solves all of these problems and is much easier to write and test than JSPs In this article I am going to look at GWT application project structure and how to write an application for creating and modifying Spring Security users as an example of how to develop applications with GWT Creating a GWT application Creating an application with the GWT plugin could not be much simpler Click the New Web Application Project button from the GWT plugin toolbar and fill in the New Web Application Project dialog Figure 1 1 Fill in the project name e g UserManager 2 Fill in the package name eg uk co marauder usermanager This is the top level package under which the Java parts of the project will be 3 Untick the Use Google App Engine as it is not required for a GWT proj
27. tried my techniques However the number of others is not statistically relevant enough nor the conditions controlled to call it a study so this remains merely a theory I encourage you to consider this material and let me know how you get on with it A few years ago I studied or more accurately started studying speed reading A significant portion of what you learn is understanding how the eye moves across the page takes information in and works with the brain to turn this into the experience we know as reading By understanding these principles we can adjust our reading style to take advantage of their strengths and play down their weaknesses As I learnt more I wondered whether the same ideas could be applied to writing as well as reading It seemed logical that if you write in a way that more closely matches how the eyes and brain read best then reading will be easier and potentially faster As I continued studying I found that this is the case One commonplace example is newspaper and magazine text This text is arranged in columns as columnar material is easier to digest by the eyes and brain when reading From here I began to wonder if this knowledge should affect the way we write code Before we look at my conclusions Ill summarise the key speed reading insights I thought would be relevant Perhaps most important is that the eyes don t move across the page in a smooth flowing manner Instead they jump in discrete fi
28. Code Critique 62 Submissions to scc accu org by Apr Ist A new version of the C standard is nearing finalisation and is partly implemented in both Microsoft s Visual Studio 2010 compiler out in beta and the latest versions of g also available on cygwin for Windows users So I thought it was a good time to present a code sample trying to use one of the new standard libraries lt regex gt I found some example code implementing a minimal subset of the well known grep command that was originally written to use the boost regex hpp library and converted it to use the new standard library I was expecting this to be a simple matter of changing the include file and some namespace names but to my surprise the code didn t work correctly on Visual Studio 2010 it compiled cleanly and at first appeared to run successfully but when I used with the i option for a case insensitive search the program failed with a runtime error C gt grep i test Error regular expression error So this issue s code is slightly unusual in that I m also providing part of the lt regex gt header to help you identify the problem As usual please also use the opportunity to comment on other parts of the code The code is in Listing 2 The relevant bits of the implementation of lt regex gt are in Listing 3 You can also get the current problem from the accu general mail list next entry is posted around the last issue s deadline or from the ACC
29. In doing so one is equipped to further show that there are six in four dimensions and just three in all other numbers of dimensions The fact that we as humans seem spectacularly ill equipped to reason about geometry in more than two dimensions is something I believe to be a consequence of the fact that we live in a two dimensional world Our retinas are two dimensional we see in two dimensions plus depth Our movement is two dimensional until very recently in our history we were more or less constrained to move only upon the surface of the Earth Small wonder that we seem to have an intuitive grasp of two dimensional geometry but are often flummoxed in three or more dimensions try to imagine a rotating a four dimensional analogue of a triangle for a clear demonstration of our cognitive limitations The transformation of a problem from one of geometry to one of algebra is almost always the easiest way to generalise it to higher number of dimension and it is exactly this approach that I have taken in trying to construct my arbitrary dimensional Delaunay triangulations Specifically I represent my multidimensional triangles with arrays of indices into a collection of points I must now try and figure out the rules for manipulating those arrays of indices such that their geometrical interpretation represents a Delaunay triangulation Unfortunately this is not an easy task since Iam not capable of intuiting the geometric operations required to
30. ListBox getItemCount i user addAuth authListBox getItemText 1 saveUser user ee Our service interface has two methods One to find users which takes a user name and returns a User object and one to save users which just takes a User object The RemoteServiceRelativePath annotation is used in conjunction with the servlet mapping element in web xml to specify the URL for the service An asynchronous interface is also required to allow the client to make calls to the service interface by specifying the callbacks used public interface UserServiceAsync void find String username AsyncCallback lt User gt callback void save User user AsyncCallback lt Void gt callback The asynchronous interface must have the same name as the service interface but appended with Async and must be in the same package Put both interfaces into the uk co marauder usermanager client package as the service interface needs to be seen by both the client and the server The server side implementation which usually goes in the server package e g uk co marauder usermanager server must both implement the service interface and extend GWT s RemoteServiceServlet Listing 10 To be callable UserServiceImp1 must be configured in web xml as a servlet The lt servlet gt element is used to give the servlet a name and specify the class that implements it lt servlet gt lt servlet name gt userManagerServlet lt servlet
31. U website http www accu org journals This helps overseas members who typically get the magazine much later than members in the UK and Europe MAR 2010 cvu 31 cvu E E US OOS ike ieime duc very ifdef USE BOOST include lt boost regex hpp gt using namespace boost else include lt regex gt if defined MSC VER amp amp _MSC VER lt 1500 A o dh Soh Urls a N a r Ie using namespace std tr1 else using namespace std endif endif include lt map gt include lt stdio h gt include lt stdlib h gt static const int MAX LINE_LEN 65536 std map lt std string bool gt option void usage printf Usage grep i 1 lt pattern gt n printf Options n printf i case insensitive n printf 1 line numbers n int process regex expbuf char buff MAX LINE LEN 1 long lineno 0 Start reading the file while fgets buff MAX LINE LEN stdin lineno bool rc regex_search buff expbuf if rc if option 1 printf li lineno printf buff return 0 int main int argc char argv regex expbuf int cflags regex constants ECMAScript if argc lt 1 usage exit 1 argvt t argc da argv Switch argv case i case l option argv break default printf i or l expected n exit 1 argvtt argc 32 cvu MAR 2010 try if
32. Vu amp Overload 807 of readers make purchasing decisions or recommend products for their organisations Reasonable rates Flexible options Discounts available to corporate members y Contact ads accu org for info MAR 2010 I cvu 7 4cvu Jez Higgins sees value in team tools for one person ike many of my programming chums I ee in the importance of the build a ae Breaking the build is a bad thing Knowingly breaking the build is well Pm not a religious man but it s a sin a Sometimes the build goes wonky or tests start failing because of mishap or misfortune Someone makes a change to one place in the code somebody else makes a change in another part something goes awry and oopsy Of course tools can help us here If you ve got something that regularly checks your source code repository for changes rebuilds g everything as soon as it does and runs your tests then you can find out if there s a problem sooner rather than later 60 count 40 20 These tools have a name continuous integration servers and are so called because they automate the process of continuous integration as described by Martin Fowler 1 You can put something together yourself pretty easily but there are any number of them available At work we ve been using CruiseControl one of the more widely used CI servers to reasonable effect over the past few months of pretty intense development We want t
33. a plane into triangles such that every vertex is one of the points All of my sources claim that such a generalisation is possible although irritatingly none of them provide any specific details on how one might go about it Neither a description of the algorithm nor my desire to generalise it are pertinent to this article so I shall provide neither I can almost hear the sighs of relief from readers sick to their stomachs of my relentless crusade to force feed mathematics to members of the ACCU I shall however attempt to impress upon you the tremendous difficulties that arise when trying to generalise an algorithm that operates in two dimensions to one that operates in an arbitrary number The difficult step is in fact moving from two to three dimensions Many geometrical properties that are blisteringly obvious in two dimensions turn out to be patently false in three If you read something in C Vu that you particularly enjoyed you disagreed with or that has just made you think why not put pen to paper or finger to keyboard and tell us about it A nice example is the fact that there are an infinite number of regular polygons polygons with sides of equal length and internal angles of equal size In contrast there are only five regular polyhedra the Platonic solids The simplest way to demonstrate that this is so is to transform the problem from one of geometry to one of algebra and to reason about numbers rather than shapes
34. a subject Understanding your particular personality type there are many MBTI tests available on the web for example will reveal specific ways to make your learning routine maximally effective Understand how you learn best Memory fades There was a time when psychologists believed that a memory once made was permanent However this is not the case a certain enzyme PKMzeta is required to keep synaptic connections valid Lose the enzyme you lose the memory 4 Our memory is also fallible in other less chemical ways The brain isn t perfect You ll notice that old memories can change and distort in your mind So it s probably not true that things aren t as good as they used to be Memories and opinions can easily warp as we recollect them to fit our current preferences or preconceived notions We can very easily implant our own false memories unconsciously or become subject to false suggestion from others In order to keep your memory active it must be refreshed constantly read and exercised If you don t need and employ a skill then you will use it 5 Use your knowledge Or you ll lose it Memory grows It was originally thought that mental capacity decreased over time that humans start off with a fixed number of brain cells and over the course of a lifetime this number decreases due to the ageing process damage caused by trauma or other abuse like excessive alcohol intake This was determine
35. act the editors cvu accu org or overload accu org cvu A Game of Strategy Baron Muncharris sets us another challenge ir R my fine fellow I must say that it does me good to see you here this winter s night Come take a glass of this warming spirit to see off Jack Frost and his mischievous cohorts As a Gentleman of sport might I tempt you to pit your purse against mine in a game of strategy Splendid It is to my shame that I entertained the remotest doubt that a man of your mettle would shy from a challenge I have in mind a game that I learnt from Feldmarschall von a dr commander of the dragon army of that greatest and most enlightened nation of Neptune East Grinstead It is employed there to train young officers in the art of placing defensive forces in the contested territory between them and West Grinstead the two nations having been formally at war following the rape of Bramber some several hundred years ago The rules of the game are simple enough I shall place a coin heads up upon a chess board and then you shall counter by placing a coin tails up upon any square other than that I have chosen Each square on the board will be deemed to be controlled by the player whose coin is closest to it as measured by the least number of moves required to move from the one to the other by a king in the noble game of chess We shall continue to take turns placing coins in unoccupied squares until we have both plac
36. ad gone before it Such paradigm shifts are the result of questioning the accepted conventions and challenging them You can t just go out and drive on the wrong side of the road or remove all handles from doors that only push either STEVE LOVE FEATURES EDITOR The official magazine of ACCU ACCU is an organisation of programmers who care about professionalism in programming That is we care about writing good code and about writing it in a good way We are dedicated to raising the standard of programming ACCU exists for programmers at all levels of experience from students and trainees to experienced developers As well as publishing magazines we run a respected annual developers conference and provide targeted mentored developer projects The articles in this magazine have all been written by programmers for programmers and have been contributed free of charge To find out more about ACCU s activities or to join the organisation and subscribe to this magazine go to www accu org Membership costs are very low as this is a non profit organisation MAR 2010 evu 1 4cvu DIALOGUE 21 Inspirational Pjarticles Daire Stockdale shares a recent source of inspiration 28 Code Critique Competition 62 Set and collated by Roger Orr 33 Desert island Books Paul Grenyer maroons Terje Sletteb REGULARS 34 Bookcase The latest roundup of ACCU book reviews 36 ACCU Members
37. and exploit that to your advantage Memory fades Unless you refresh your knowledge by using it your memory of it will become unreliable m Memory grows Constant stimulation is required to maintain growing mental capacity Mental state effects learning Cultivate a positive attitude towards learning Otherwise you may as well not bother m Learning models Certain models can help us classify levels of expertise and plan how to gain it When I set out to write this column I intended to talk about a number of quite specific techniques that will help us to learn better and explain the above topics briefly as background material to justify the techniques As you can see I ve hardly gone into any detail and yet I ve filled many inches of magazine space 6 cvu MAR 2010 OK now let s look at a scenario where the road making machines have been busy during the wedding ceremony and have widened the highway to a two lane affair fast machines and slow grooms This time the cars line up two abreast and set off It still takes the same time for the first cars to get there 16 minutes but since they are arriving two at a time it only takes half the time six minutes between the first and last car s arrival giving us four cars minute That makes a total of only 22 minutes for the whole caboodle Of course if we had a six lane highway we could get all the cars through in two minutes bringing the total time down to 18 min
38. and those of you who have attended weddings will know that this is serious and can cause undying feuds So we now have latency throughput and jitter How do these apply to the Internet Well modern networks divide the stuff you are sending or receiving into packets of data the cars and send them off to their destination Network latency is considered to be the time it takes for you to send a packet and to receive an answer a round trip rather than the one way trip we used throughput is considered to be the amount of data you send each second usually measured in bits second and jitter is a measure of the difference in time between the arrival of packets And how does it affect you Well if you are playing an online game the most important factor is latency lag in the common game parlance The longer it takes for you to get a response to your command from the game the more difficult and frustrating it is to play Of course the acceptable lag latency is different for different types of games For a turn based game a lag of several seconds will not make any appreciable difference but for an on line shoot em up even a few tens of milliseconds can be too much A lagged combat flight sim will have you shooting at opponents who are no longer actually in sight even though most flight sims are slowed down by a factor of at least four The normal way to handle this is to use a probabilistic method of determining whether th
39. at a finite speed so longer routes will take a longer time There are solutions of course and the most common is buffering you don t start playing the video until you have a chunk of it already downloaded so you are never in a state where the next packet isn t already there and each packet can be displayed at the correct time Unfortunately you can t delay people s phone calls in this way which is why Voice over Internet Protocol VoIP can still be a little on the ropey side CERTIFICATE IN QUANTITATIVE FINANCE Expand Your Mind and Career Designed by quant expert Dr Paul Wilmott the COF is a practical six month part time course that covers every gamut of quantitative finance including derivatives development quantitative trading and risk management Find out more at cqf com So now you have more than you ever wanted to know about latency throughput and jitter Think of it as a little something for you to use to demonstrate your superiority at both dinner parties and wedding receptions especially if you are the best man Confession this started life as a short piece in my weekly newsletter Winding Down I ve rewritten and extended it for this rag Normally I write fresh stuff for CVu but this issue I plead a stinking cold striking just as the deadline came up and exhaustion from having to actually work and commute yes surprise surprise I finally got a job m Advertise in C
40. at is the one true way when it comes to formatting function signatures Well apart from one true way being an overstatement I m going to leave my specific recommendation for a subsequent article how else could I get you to come back Before I finish for now I want to come back to the issue of how important this all is in the first place We touched on three areas that I believe are worthy of consideration m The overhead of reading code unoptimised for reading may be more significant than we realise due to the subconscious processes that are at play not just in time but in energy and focus m Even relatively small interruptions to our state of flow can have a noticeable impact on our productivity Sometimes it can even become a serious bottleneck think butterfly effect m Having a consistent style may actually speed up code writing time but optimising that style for the way our eye brain connection works can lead to significant increases in code reading comprehension time In the next articles I will present my recommendation for function signature formatting and return once again to the question of how much difference it makes including some anecdotal evidence W C Vu and Overload rely on article contributions from members That s you Without articles there are no magazines We need articles at all levels of software development experience you don t have to write about For further information cont
41. ath although it is strongly recommended that they appear in the root package of a standard project layout The XML Module file generated for the UserManager project UserManager gwt xml looks like Listing 1 and m Defines the name of the module for the project usermanager m Inherits the required GWT modules E com google gwt user User E com google gwt user theme standard Standard m Specifies the entry point class E uk co marauder usermanager client UserManger m Tells the GWT compiler where to find the source files it needs relative to the module XML file client HTML host pages GWT modules are stored on a web server as a set of JavaScript and related files In order to run the module it must be loaded from a web page of some sort Any HTML page can include a GWT application via a SCRIPT tag This HTML page is referred to as a host page from the GWT application s point of view A typical HTML host page for an application written with GWT from scratch might not include any visible HTML body content at all The UserManager host page UserManager htm1 looks like Listing 2 GWT was designed to make it easy to add GWT functionality to existing web applications with only minor changes It is possible to allow the GWT module to selectively insert widgets into specific places in an HTML page To accomplish this in the example above the id attribute is used to specify a unique identifier that your GWT code will use to attac
42. ation of a soft skills topic the previous instalment of this column we began a journey of self one that is very often radically under appreciated in our field In the last issue we considered the importance of learning to our craft Software developers are in the knowledge business We re not mechanical automatons doing the same thing over and over We re constantly solving new problems and facing new challenges We re continually acquiring information using information and generating information We must therefore be able to learn constantly or it s Game Over We must ensure that we know how to learn We also thought a little about what to learn This list includes technology and technical skills as well as softer skills e g team working It also includes more left field non programming topics we need a broad world view to inform our technical decision making processes Learning basket weaving might just give you valuable insights into your day job The facts of life Here are a few facts that provide some useful context to the world of learning Learning is a basic human skill We all do it We just do it in different amounts Small children are constantly learning and amassing new skills Language cause and effect and social skills are picked up rapidly from birth As are basic physiological capabilities like eating walking and continence Although continence might also be considered a social skill of
43. b Developer Tools 4 Click next and follow the install instructions Restart Eclipse when asked Installing the GWT plugin is much the same process 1 Go to the Help menu and select Install new software 2 Add the update url http dl google com eclipse plugin 3 5 or the apropriate link for your version of Eclipse 3 Tick Google Plugin for Eclipse 3 5 and Google Web Toolkit SDK 2 0 0 Untick Google App Enginer SDK 1 unless you particularly want to install it It is not needed for the GWT plugin 4 Click next and follow the install instructions 5 Restarted Eclipse when asked More detailed instructions can be found on the Google Plugin for Eclipse 3 5 Galileo Installation Instructions 12 page of the GWT website 1 Model View Controller http www marauder consulting co uk Model View_Controller pdf Apache Struts http struts apache org Google Web Toolkit http code google com webtoolkit NO Apache Tomcat http tomcat apache org Pee es Ce on Organising Projects Development Guide http code google com webtoolkit doc latest DevGuideOrganizingProjects html 6 Data Access Layer Design for Java Enterprise Applications http www paulgrenyer com Data Access Layer Design for Java Enterprise Applications pdf 7 Swing Layout Managers http java sun com docs books tutorial uiswing layout using html 8 Download Data Access Layer project http paulgrenyer net dnld dataaccesslayer zip 9
44. const version may be provided that uses the usual add remove const trick making the value part modifiable if it is needed Understanding the design constraints should make the code evident so just a light explanation m Private typedefs are for convenience map binds both key2 and value to key1 and the stock pair is used instead of a custom struct backmap provides the reverse lookup of the keys m The find functions are the error filters to be used when we expect the key be there unfortunately map has no const operator that would do that stock E insert is similar to the original code s version but first makes sure to clean up and leaving no doubt of the possible post condition ati1 does the obvious thing and at2 just looks up the first key to be usable with at1 m the erase operations do nothing if the key pair is not there and remove the entries from both maps otherwise E size now makes sense as all operations ensure the two maps have the same element count This is good for a reference version that does the job but has many redundant lookups To cover those a different implementation can be created The code in Listing B is supposed to replace the marked section in the first version Importantly it has the very same public interface and MAR 2010 evu 29 cvu shall work with the same test suite The goal was to keep lookups to the minimum It is easier to understand and review having t
45. creating and editing Spring Security users using a slightly modified version of the data access layer I developed as part of my Data Access Layer Design for Java Enterprise Applications 6 article In the article I created a class to model a Spring Security user and wrote a data access layer capable of serialising it to and from a database Listing 5 shows a slightly modified version of the class The modifications required are making all the setters public and the whole class serializable using the GWT IsSerializable marker interface This is because as we will see shortly we need to be able to use Dozer a Java Bean to Java Bean mapper that recursively copies data from one object to another to make a copy of the class and have it serialised between the client and server The User class has fields for a user name password enabled flag and a list of authorities Therefore the user interface for creating and editing Spring Security users needs to have an equivalent widget for each plus a button for saving users a button for finding users buttons for adding and removing authorities and an edit box for entering authorities to add To start off with we need a basic GWT application and the UserManager project is ideal If you have not done so already create it and remove the following files as these are an example of how to implement remote procedure calls and are not needed a GreetingService java a GreetingServiceAsync java a GreetingSer
46. d Books continued scope than Alexander s book The Timeless Way of Building so it s not considered further here One of my favourite books of all time is Richard Bach s Jonathan Livingston Seagull which definitely is a good candidate for a novel to bring However it s quite short it can be read in one sitting more or less which is a great thing but perhaps not so great for a potentially very long stay at a desert island For the novel or non technical book I d like to include something that goes beyond mere technical stuff something that talks about life itself about personal development Something that I could ponder on those long nights at the desert island For this I d like to include some spiritual philosophical stuff from either Richard Bach or Peter Russell and I d hope that Paul would be lenient in letting it pass as a novel ve recently bought several books by Peter Russell and his background with a Ph D in theoretical physics as well as his spiritual journey gives him a quite interesting background something missing in most pseudo scientific books in this genre He s written several interesting looking books including Waking Up in Time Finding Inner Peace in Times of Accelerating Change and From Science to God and based on what I ve read of him before such as Passing Thoughts a booklet he published many years ago now partially available on the Intern
47. d by scientists studying animals in laboratory cages they saw no sign of neurogenesis the growth of brain cells But this was simply because a brain devoid of stimulus need make no new connections cvu The test subjects brains didn t expand because there was no need to life in a cage stunts brain growth That s a pretty damning indictment of modern cubicle working In the early 1990s psychologist Elizabeth Gould discovered that in suitable conditions an environment with stimulation and opportunities to interact and learn the brain is perfectly capable of growing neurons and making new connections 6 Other subsequent studies have drawn links between exercise and increased brain growth So that s good news you have a practically limitless ability to expand your mind And the scientists have proved that you need stimulation do to so Break out of your cubicle and feel free to drink a beer Mental state effects learning Factors such as stress and a lack of sleep will clearly contribute to an inability to concentrate and so will degrade your ability to learn Your mental attitude also dictates how well you will learn Psychologist Carol Dweck s research 7 shows that students who believed that they couldn t increase their knowledge were not able to do so Those who believed they could increase their mental capability were easily able to Believe in your ability to learn People who enjoy learning naturally l
48. d for that invokes an extra search for the already found element That hardly makes sense unless multimap was used The placement of erase key is off too normally it should either follow the loop or being followed by a break On my reviews even a fraction of discovered problems would invoke square 1 and for a fix we better really go back to the design table Not having the requirements I make up some to show a solution route The one in Listing A is created as a version to be easily read and verified against expectations Beyond juggling with first and second m The class is called twokey_map better describing the purpose m The template has a third argument to allow different types for the two keys with the default of using the same type so usage is similar to the original with no real cost and even more clarity in the code m The state is held in two maps without pointers or any other hard cross reference One binds key1 to key2 and the other backwards So we can find out the key pair having either of the keys and by a simple map lookup The first map also stores the value to avoid another map with the same key m The design rule of the state here is that the key pairs are exclusive instances of key1 have 1 1 relation to those in key2 that is enforced in both insert and erase operations m fetch operations are const key wise attempt to ask a key not stored is an error signaled by exception here A non
49. dget less The info command also searches online information this time in usr share info The twist is that the info pages are an early form of hypertext Typing in the command info brings you into the top level IAN BRUNTLETT On and off lan has been programming for some years He is a volunteer system administrator for a mental health charity called Contact www contactmorpeth org uk As part of his work lan has compiled a free Software Toolkit http contactmorpeth wikispaces com SoftwareT oolkit 26 cvu MAR 2010 of the info tree and gives information to guide the user through info s particular interface The apropos command searches the man pages for relevant pages It is identical to running man k keyword but I learnt to apropos long before finding out about man k Testing regular expressions regexps Regexps 3 4 can get very complicated and therefore difficult to test The simplest test can be made from the command line using two commands echo and grep short for global regular expression print echo The quick brown fox grep o This could be tested on a more industrial scale by processing a whole file of lines using the command grep lt expression gt test input txt For example here is my test input txt The quick brown fox jumped over the lazy brown dog The quick brown fop jumped over the quick brown fox Humpty Dumpty could not be put back together again ian Ruther
50. dson could be configured entirely though its GUI I m slightly ashamed to say that s the reason why I gave it a try but I m glad I did Hudson is extremely easy to fiddle with setting up builds chaining different builds together tool integration and so on are all straightforward and can be done via a web browser I doubt there s anything it can do that can t be done with CruiseControl but for exploratory work it s streets ahead Jez works in his attic which was recently replastered living the devil may care life of a journeyman programmer He is currently learning to tumble turn without getting water up his nose His website is http www jezuk co uk 8 cvu MAR 2010 100 i a a a oe a a a me a om a a a om me a a a a E E T ns eRe Re eee T TH EP eee a g Most of the time I work remotely accessing work machines over Citrix It sufficient most of the time but the Citrix connection isn t exactly snappy and that becomes a little frustrating when you need work across it for an extended period Because at the time I was more interesting in finding out about Hudson than anything I installed it on my own server The network latency between my desktop machine and the server by my left ankle is always going to beat Citrix So I had Hudson and I needed some code Fortunately I had some of that too From a standing start to building my Mango library 2 of Java bits and bobs and running its tests via instal
51. e bullet has hit The easiest way to visualise it is to think of a cone of probability of bullets hitting rather than a stream of single bullets Unless of course you are lazy in which case you offload the work to the client instead of doing it at the server You will then find yourself in an arms race with your players who will repeatedly hack the client to give themselves an advantage If you are downloading a large file the important factor is throughput Large files have hundreds of thousands of packets A several second initial lag when you ask for the file is nothing compared to the tens of minutes it takes between the first packet to arrive and the last one The more packets you can get through the pipe at the same time the more lanes the shorter the download Finally jitter matters if you are receiving streaming video and audio In video if the packets are arriving at slightly different intervals and you are watching them in real time then the picture will appear jerky In audio the voice or music is distorted by the timing Partly this is caused by congestion and partly it s in the nature of the internet which you should think of as being like a fishing net where computers and routers are each knot rather than two tin cans with a piece of string stretched between them In the internet different packets can take different routes some of which are longer than others and as we all know from school physics even light travels
52. e highway that just happens to go from where the party are now to the hall where the reception 1s being held As luck would have it the highway is empty and the cars are able to proceed single file at top legal speed 70 miles hour where I come from to the reception The time it takes each car to get to the reception let s say 16 minutes is the latency Of course getting the whole party there takes longer than that because the cars are spaced out for safety so let s say it takes another 12 minutes between the time the first car arrives and the last one discharges its passengers This is the throughput two cars minute So in this scenario it takes a total of 28 minutes from the time the first car departs to the time the last car pulls in the passengers get out and we can toast the happy couple with Verve Clicquot NV champagne Live to Love to Learn Part 2 continued Our learning is too narrowly focused Consider a wider sphere of reference Draw inspiration from other fields Learning is hard work It doesn t come for free But you don t get a reward without an investment Learn to learn That s why I m writing this series The most effective learning is done on purpose and planned to maximise effectiveness m The left brain right brain split We need to employ all of our available brainpower to make our learning maximally effective m Personality type affects learning style Understand how you best learn
53. e of thinking 2 The left hemisphere tends to govern analytic and logical activities language symbolic representation rational deduction the linear thought process whilst the right hemisphere performs non linear processes characterised as non rational spatial holistic and identifying spatial relationships The common view is that people rely more or tend towards using one side of their brain rather than other Artistic creative types favour their right brain academics and office workers favour the left Apart from reinforcing a social stereotype this is not strictly accurate since the split of brain activity is not pure laterally biased Several psychologists have since tried to come up with other terms but popular culture has latched on to left and right and we re stuck with them The common view is that people rely more or tend towards using one Side of their brain rather than other Both parts of our brain and both modes of thought are essential In order to think and learn effectively we must be able to bring both sides of our brain into use Since programmers tend to lean towards the left brain mode of operation we must learn to introduce more right brain thinking into our 4 cvu MAR 2010 regimen this requires us to find ways to dial down our left brain activity to give the other side a fighting chance We ll see some ways to do this later There s a lot more that could be said on this subject
54. e the object to be copied needs to be checked for nu11 first If you run the application now you will be able to both save and find users The basic functionality of the application is now complete If you look back at Figure 5 you will see that the main problems with the layout are the buttons being different widths and the authorities list box not being the same width as the text boxes This can all be fixed with CSS Replace the contents of the existing UserManager css file in the war s WEB INF directory with the Listing 15 and refresh the application in the browser There is no need to restart the application to apply CSS changes You will see that all the text boxes and the list box are the same width and all the buttons are the same width Most GWT widgets have a default style name such as gwt TextBox or gwt Button These are used in the CSS file to specify things like font size and widget width The GWT Grid widget does not have a default style name so one must be added manually using the setStyleName method It also does not have a way to specify the cell alignments in CSS so this too must be done manually by subclassing Grid in a similar way to ListBox Listing 16 The constructor as well as assigning a style name iterates through each cell in the grid and sets the vertical and horizontal alignment Figure 6 shows the far more aesthetic version of the application with the CSS changes f iii User Manager Mozilla Firefo
55. earn more People who want to learn learn more Is this the power of mind over matter Perhaps it 1s and it s something we need to exploit I ve long argued that our attitude effects the quality of our work This is the central theme of my book Code Craft 8 Learning models There are a number of very illuminating models of learning that have been constructed by educational psychologists The Dreyfus Model of Skill Acquisition is a particularly interesting example postulated by brothers Stuart and Hubert Dreyfus in 1980 whilst they were working on artificial computer intelligence 9 After examining highly skilled practitioners in fields such as airline pilots and chess grand masters they identified five specific levels of understanding m Novice A complete newbie Novices want to get results fast but have no experience to guide them in doing do They look for rules they can follow by rote and have no judgement to tell whether those rules are good or bad Given good rules or luck finding suitable resources on Google novices can get quite far Novices have no knowledge of a topic yet m Advanced beginner At this level some experience that has lead to learning you can break free from rules a little and try tasks on your own But perception is still limited and you ll get stuck when things go wrong At this level there is a better understanding of where to get answers you know the best API references for example but you a
56. ect 4 Click Finish to create the project This will create a project called UserManager If you are keen to see what a GWT web application looks like it can be run in the normal Eclipse way by selecting the project in Eclipse s Project Explorer and clicking the green run arrow This will open a development mode window containing a URL similar to the following http localhost 8888 UserManager html gwt codesvr 192 168 106 1 9997 The web application is running in an embedded webserver and can be accessed by pasting the URL into a browser The first time you do this you will need to follow the instructions to install the GWT Developer plugin Once the plugin is installed and your browser restarted the Web Application Starter Project which is the default GWT project is displayed see Figure 2 It consists of a title and edit box with a label and a button Clicking the button sends the contents of the edit box to the server via PAUL GRENYER An active ACCU member since 2000 Paul is the founder of the Mentored Developers Having worked in industries as diverse as direct mail mobile phones and finance Paul now works for a small company in Norwich writing Java He can be contacted at paul grenyer gmail com 16 cvu MAR 2010 New Web Application Project gt eles Create a Web Application Project Create a Web Application project in the workspace or in an external location Project name UserManager Package e
57. ed three coins on the board If after we have each played our three coins I control more squares on the board than you then I shall have won the game and may take all six coins as my bounty To counter the advantage I have in playing first you shall win and take the coins if you control a greater or equal number of squares as I Now I feel it is only fair to warn you that I have something of a natural talent for strategy Indeed after having bested every officer in training I was immediately given the rank of Oberleutnant and dispatched to defend the border This was of course during the well reported escalation of hostilities that arose after East Grinstead beat West Grinstead 13 knees to 3 in the Neptune International Cup and the subsequent accusations that the former had been wearing illegal performance enhancing lederhosen The account of how I diffused the situation and averted all out war with a well timed witticism regarding the peoples of Saturn is a tale for another evening I explained these rules to that witless student whom it is my very great misfortune to know and he started babbling on about the strangulation of some poor fellow called Delaney during a discreet duel with Lord Fauntleroy Not a minute later he admitted that his story probably had little bearing on the playing of this game a fact so transparently self evident that it should have been clear to all but the most feeble of minds Now sit here and take another glass
58. ee members duly proposed seconded and accepted shall be lodged with the Secretary at least 14 days prior to the General Meeting and 7 7 In addition to written nominations for a position nominations may be taken from the floor at the General Meeting In the event of there being more nominations than there are positions to fill candidates shall be elected by simple majority of those Members present and voting The presiding Member shall have a casting vote For historical and logistical reasons the date and venue is that of the last day of the ACCU Spring Conference Please note that you do not need to be attending the conference to attend the AGM For more information about the conference please see the web page at http accu org conference More details including any more motions will be announced later A full list of motions and electoral candidates will be supplied at the meeting itself Alan Bellingham Secretary ACCU
59. et these are probably both good Desert Island Disks is one of Radio 4 s most popular and enduring programmes The format is simple each week a guest is invited to choose the eight records they would take with them to a desert island http Awww bbc co uk radio4 factual desertislanddiscs shtml The format of Desert Island Books is slightly different from the Radio 4 show You choose about five books one of which must be a novel and up to two albums Some people even throw in the odd film Quite a few ACCUers have chosen their Desert Island Books to date and there are plenty more to go The rules aren t too strict but the programming books must have made a big impact on your programming life or be ones that you would take to a desert island The inclusion of a novel and a couple of albums helps us to learn a little more about you The ACCU has some amazing personalities and Desert Island Books has proved we only scratch the surface most of the time Each issue of CVu will have someone different If you would like to share your Desert Island Books please email me paul grenyer gmail com 34 cvu MAR 2010 By Mike Gancarz published by Digital Press ISBN 1 Linux and the 55558 273 7 3 Unix Reviewed by lan id E Philosophy Bruntlett AY Highly recommended This book should have been sub titled Anagathics for programs and data anagathics are medicines which inhibit aging I find that
60. ford wrk grep E fo test input txt The quick brown fox jumped over the lazy brown dog The quick brown fop jumped over the quick brown fox Testing and developing complex pipelines Here is an example of a slightly complex pipeline that lists programs in sorted order ps x awk print 5 4 sort It s not that complicated and I built it up step by step at the keyboard However there are times when a tool could make life easier There are two particularly useful commands cat and tee The tee command peeking into a pipeline Similar to the cat command see next paragraph tee copies its input stdin to its output stdout However it can be told to duplicate the data flowing through the pipeline By giving a filename as a parameter tee will 1 copy its input stdin to its output stdout and 2 send a copy of that data to the named file The cat command injecting a file into a pipeline I usually overlook the cat command preferring to use the more command to see a text file page by page The parameters passed to cat tell it what to output In its simplest form cat wibble txt simply copies the contents of wibble txt to its output stdout There can be more parameters passed to cat e g cat wibble txt dibble txt would instruct cat to copy the contents of wibble txt to its output stdout followed by the contents of dibble txt However cat has a special ability A parameter can either be a filename
61. g related activities too such as solving certain types of problems or extracting relevant details from a sea of information It s almost like offloading some heavy number crunching to a GPU then finding that your refresh rates are suffering Another factor is the concept of flow When we are thinking about one problem and we are focused on it we are in a certain flow The more we are then distracted by the mechanics of the task consciously or subconsciously the more it can knock us out of the the flow Again we may be so used to this that we hardly notice Pay attention next time you are stuck in a problem and you find yourself losing track the more you have to hunt around through the code In summary we need to get out of the trap of just looking at the numbers a second here a few milliseconds there They may bear little relation to the real factors at play There s more we can learn from the world of speed reading and eye brain coordination but we now have some things to go on that can lead us to conclusions about code formatting First the way eye fixations are able to take in multiple words both horizontally and vertically suggests that islands of related code should be readily assimilated in one or two fixations Such islands can be created through logical grouping and effective use of whitespace both to separate from other islands and for alignment purposes Alignment touches on char txt hello int i 7 std
62. g the getSelectedIndex method and removed from the authorities list box using the removeItem method If you run the application now you will see that when you type an authority into the authorities text box the Add button enables and clicking it inserts the authority into the authorities list box Selecting the authority in the list box enables the Remove button and clicking it removes the authority from the list box However the Remove button remains enabled even when there are no selected authorities in the list box This is due to the change handlers not getting called when items are inserted or removed from a list box This is by design as GWT assumes that you know when you are inserting or removing items from a list box as you are explicitly calling insertItem or removeItem This is not the behaviour that we want though To get the behaviour we want we need to inherit from com google gwt user client ui ListBox and override insertItem and removeItem and modify the implementations so that they cause the change handlers to be called To do this create a package called uk co public class ListBox extends com google gwt user client ui ListBox Override public void insertItem String item int index super insertItem item index ChangeEvent fireNativeEvent Document get createChangeEvent this Override public void removeItem int index super removeItem index ChangeEvent fireNativeEvent Document get
63. h widgets to that HTML element The UserManager host page ous DSE Edit Navigate Search Project Run Win a 2 UserManager a G sre 4 B uk co marauder usermanager x UserManager gwtxml 4 6 uk co marauder usermanager client J GreetingService java J GreetingServiceAsync java J UserManager java 4 6 uk co marauder usermanager server gt J GreetingServicelmpl java 4 BA GWT SDK GWT 2 0 0 fag gwt user jar gt fad gwt dew jar gt Ba JRE System Library jre6 gt test a war a WEB INF 4 amp lib E Qut servletjar ix web xml UserManager css UserManager html E y m Specifies a style sheet called UserManager css which is also generated as part of the project Sets the page title Includes the JavaScript generated for the module by the GWT compiler usermanager nocache js lt html gt lt head gt lt meta http equiv content type content text html charset UTF 8 gt lt link type text css rel stylesheet href UserManager css gt lt title gt Web Application Starter Project lt title gt lt script type text javascript language jJavascript src usermanager usermanager nocache js gt lt script gt lt head gt lt body gt lt h1l gt Web Application Starter Project lt h1 gt lt table align center gt lt tr gt lt td colspan 2 style font weight bold gt Please enter your name lt td gt lt tr gt l
64. he first version in practice it is a good idea to have solid code before doing optimizations m The first map is kept the same and as it did the whole job optimally on keyl using functions The other map now stores an iterator to the first map as the value instead of the key itself so lookups in the first map are avoided We can do that because the other design constraints ensure proper pairs with the same lifetime no ugly cases for invalidated iterators The find functions left a single use and got inlined at1 is really the same as before just losing a readability point to a missing abstraction barrier at2 fetches the iterator to the first map ready to use nuking one key lookup m The erase functions stayed exactly with the same source thanks to our typedefs and the luck that map s erase has an overload and the code switched to the one taking iterator from one taking the key The massive looking change is in the insert member Demonstrating how simplicity is flushed as we try to squeeze operations Content from erase is getting inlined so we can capture some of the internal state If the entry for key1 is present it is no longer removed then inserted but just reassigned in place A test suite is not provided to save space Listing A include lt map gt include lt utility gt include lt stdexcept gt class to map a value to two alternative keys template lt typename KEY typename VALUE t
65. http en wikipedia org wiki Myers Briggs_Type_Indicator Brain Researchers Open Door to Editing Memory in New York Times http www nytimes com 2009 04 06 health research O6brain html r 1 Use it or lose it Neurogenesis in the Neocortex of Adult Primates Elizabeth Gould Alison J Reeves Michael S A Graziano Charles G Gross in Science 15 October 1999 Vol 286 no 5439 pp 548 52 Mindset The New Psychology of Success Carol S Dweck Ballantine Books ISBN 0345472322 Code Craft The Practice of Writing Excellent Code Pete Goodliffe No Starch Press ISBN 1593271190 A Five Stage Model of the Mental Activities Involved in Directed Skill Acquisition Stuart E Dreyfus and Hubert L Dreyfus Storming Media Available from http handle dtic mil 100 2 ADA084551 only takes eight minutes for the first cars to arrive if you happen to have a six lane highway the total time comes down to ten minutes from start to finish That s not bad And jitter Now this is interesting In this case imagine everyone has been sloppy about setting their cruise controls so that the speeds of the individual cars are slightly different Not a lot different just a tiny difference This means that by the time the cars arrive they are just a little bit out of formation and the time between the arrival of each car is slightly different We call this difference jitter If the jitter is really bad some cars might arrive out of order
66. ial There may well be something more inspiring struggling to get out In all honesty I can t recommend this book as it stands I would suggest that unless you have a burning need to understand Hadoop instantly you wait for the second editions of the current Hadoop books to come out If you do need instant material then you need to find a real bookshop i e not Amazon browse through and compare the three books that seem to be available on Hadoop and pick the one that most suits you Not recommended visit WWW accu org for details MAR 2010 lt cvu 35 Membership news and committee reports View From The Chair Jez Higgins chair accu org In an indicative example of my occasionally chaotic approach to planning and deadlines I ve been mentally preparing to write my last View From The Chair A last minute review of the copy dates shows that unless the new Chair is escorted from the AGM on the 17 of April and has their feet held to the fire until they ve written something I ve got one more to go I can t really complain though because it s one of the few obligations of being Chair Many aspects of the organisation run themselves Take accu general for instance which is almost entirely constructive and polite if occasionally given to a pun too far There is work involved in running ACCU though and the bulk of it is done by Alan Stewart Mick and Tony respectively our Secretary
67. iceAsync java and GreetingServiceImp1 java is mostly related to making a Remote Procedure Call RPC and displaying a dialog box which I will describe in more detail later The WAR directory The war directory is the deployment image of your web application It is in the standard expanded war format recognised by a variety of Java web servers including Tomcat Jetty and other J2EE servlet containers Table 1 It contains a variety of resources m Static content you provide such as the host HTML page m GWT compiled output m Java class files and jar files for server side code a A web xml file that configures your web app and any servlets lt xml version 1 0 encoding UTF 8 gt lt DOCTYPE web app PUBLIC Sun Microsystems Inc DTD Web Application 2 3 EN http java sun com dtd web app 2 3 dtd gt lt web app gt lt welcome file list gt lt welcome file gt UserManager html lt welcome file gt lt welcome file list gt lt web app gt The web xml file is worth looking at in a little more detail Listing 4 In its most basic form web xm1 specifies the default or welcome HTML page For the UserManager project it also tells the servlet container how to handle RPC calls but as I am going to look at that in more detail later I have omitted it here Writing web applications with GWT To demonstrate how to write a web application in GWT I am going to work through an example and develop a front end for
68. ike calling any method on any object however you need to give it an implementation of the appropriate AsyncCallback interface Listing 11 private void findUser final String username userService find username new AsyncCallback lt User gt Override public void onFailure Throwable caught Window alert caught getMessage Override public void onSuccess User user if user null updateUser user else Window alert Could not find username cvu The AyncCallback interface has two methods you must implement onSuccess and onFailure The onFailure method is called if there is a failure on the server side such as an exception being thrown and passes the failure back as a Throwable object This object can be queried and the error message displayed to the user in this case by way of an alert message box The onSuccess method takes a parameter of the type specified as AsynCallback s generic parameter This is the object returned from the RPC call All objects passed to or returned from RPC calls must implement the GWT IsSerializable marker interface have a default constructor which can be private and be visible to the client and server side RPC calls are entirely asynchronous so calls return immediately and the AsynCallback methods are called sometime later In this case if the user has been found anon null User object is passed back and then passed on to the
69. in some maxims or leave them to weave new information into their broader understanding Note than the Dreyfus model applies per skill You may be an expert in a particular topic and a complete notice in another This is natural And should also be a source of humility even if you know all there is to know about Behaviour Driven Design you may no nothing about the Joe Bloggs Test Framework It should excite you that there is something more to learn that may enhance your expertise in BDD whilst keeping you humble that you aren t an infallible expert in every subject No one likes a know it all Shu Ha Ri is another interesting model of learning that originates in Japanese Martial Arts It is a set of three terms describing the stages a student goes through to to achieve mastery in their discipline roughly translating to Learn Detach Transcend In the Shu phase the student studies under one teacher he does not understand enough to mix concepts from different streams but aims to imitate the teacher precisely He must build up experience in the field absorbing the teacher s explicit and tacit knowledge Once he has a full understanding of the techniques the student reflects on them in the Ha phase The knowledge he has learned will not change but he can interpret reflect and explore the deeper meaning Finally the student progresses to Ri where he moves beyond studentship he has original thoughts and becomes a master himself
70. ing 2 I would bet that for the majority of c c developers spotting the missing in the second example was faster and perhaps even more automatic than in the first Even if you agree with that you may wonder still how much that matters We re talking seconds or perhaps milliseconds difference in time And that leads us to another cliche The majority of development time is spent debugging code rather than writing it PHIL NASH Phil Nash has been coding for 29 years and getting paid for much of the last 19 of them working with C and related languages including C Java and Objective C He runs a blog at http www levelofindirection com and can be followed on Twitter as phil_nash 10 cvu MAR 2010 int main int argc charargv printf hello world n This is often wheeled out when encouraging use of longer more descriptive identifier names or the use of a more verbose but explicit way of doing something Actually those areas are somewhat related to our topic but here the point is if actual coding time is a small part of overall development time do a few milliseconds here a second or two there make any difference and remember that was a fairly extreme case These are all good questions I m now going to explore some possible answers for them What I m going to present here is my own view based on my own experience and research as well as the experience of a number of others that have
71. ing level than I do and Ash had sent me a few patches to silence various things he was seeing Setting up Hudson to build Arabica took again only a couple of minutes even though it s a C project using Autotools rather than a Java project using Ant I cranked up the warning level 600 hundred warnings Blimey count I suspect that Hudson s GCC warnings parser isn t quite as refined as the Java warnings parser so I don t believe that was the true number Nevertheless it was still a lot and rather more that I was expecting They were gone in 15 builds Figure 2 All of them gone I didn t have to make 600 individual fixes a change in an include file can wipe out several warning messages at a stroke but I think that s pretty quick And I know ll keep those warnings at zero too 100 In the next few days I hacked Arabica s test suite to generate JUnit compatible output Now Hudson tracks those for me too as shown in Figure 3 Another plugin prompted me to add in Cobertura test coverage analysis to the Mango build Hudson charts those results too If you look at Figure 4 carefully you ll see the lower line starting to trend up I installed Hudson on my server so I could fiddle around with it a bit expecting to throw it in a couple of days I didn t expect that it would creep into my b
72. ing statements that should be true but rather for checking statements that must be true The distinction is principally that the former are not within the control of your own code and the latter are Any requirements that can be broken by a client using the public interface to your code be that functions declared in a header file or public member functions of a class or by interaction with external libraries and or resources fall into the former and are rightly handled with a fully featured error mechanism such as exceptions Any requirements that are logical consequences of the correct implementation of your code are rightly handled with asserts The most obvious example is the use of asserts to describe pre and post conditions of any non public functions used to abstract away implementation details of functions in the public interface to your code As such they serve as a kind of compiler enforced documentation to assist future maintenance not as powerful as that provided by languages like Eiffel but useful nevertheless Now I am reasonably certain that I haven t raised any points that aren t already well known However I have recently been exposed to another use of assertions that I suspect is not so widely disseminated Iam currently trying to generalise an algorithm for constructing Delaunay triangulations from the plane to an arbitrary numbers of dimensions A Delaunay triangulation is a unique scheme for connecting points in
73. ise around traffic islands Even as a pedestrian when crossing a two way road you naturally and automatically expect traffic in a particular o much about the way we interact with the world S around us is driven by convention Sometime those conventions have side effects for example driving on a particular side of the road In a country where it is conventional to drive on the left it s also by implication conventional to drive around traffic islands clockwise Going against convention has consequences ranging from mild to severe but you d be very lucky indeed to escape without any consequences at all lane to be travelling in a particular direction and when cars are on the wrong side of the road crossing that road takes a bit more thought So it is with programming When we read code in a particular language we naturally and automatically make assumptions about its behaviour according to the idioms of that language For example in Python member functions it s conventional to use self to refer to the current object instance It s not enforced but it would cause most Python programmers significant confusion if you were to write this instead even though it s entirely legal to do so Deliberately going against convention can have positive consequences however When it was introduced by Alexander Stepanov the C STL went against a huge body of accepted wisdom for container and algorithm libraries that h
74. ist for the desert island There s still room for one more technical book The Science of Programming by David Gries thanks to Hubert Matthews for recommending this book many years ago is a clear candidate I sense this is also a great book but it requires quite a bit of in depth study and contemplation so I ve only started reading it A desert island would be a perfect place to go deeply into this one That the foreword is written by Edsger W Dijkstra is quite telling This is a tough call as another book I d like to re read is Domain Driven Design by Eric Evans which is also one of the best books I ve read However given the tough constraints on technical books for the desert island and that I ve already read Domain Driven Design Gries 1s in and Evans is out Now for the novel After all this hard core technical stuff it would be nice with a novel or two to balance things The More Than Complete Hitchhiker s Guide to the Galaxy would be an obvious candidate for me and it cleverly includes four of the five books in the Hitchhiker trilogy so it could count as one book in this context However given that I ve already read it twice it ll have to face some competition It may not count as a novel but it s not a technical book either and that is The Timeless Way of Building by Christopher Alexander by many regarded as the father of the patterns movement and the book that really started it
75. iversity then it must be correct But consider who paid to write the book or who funded the research What are their motives driven by Many things presented as fact in the most prestigious journals are in fact opinion and conjecture backed up by slim arguments For example 70 of PETE GOODLIFFE rn Pete Goodliffe is a programmer who never stays at the same place in the software food chain He has a passion for curry and doesn t wear shoes Pete can be contacted at pete goodliffe net MAR 2010 cvu 3 4cvu everything I ve written up to this point was made up Including that statistic Be aware that you can learn the wrong thing and believe it s the right thing This can be at best embarrassing and at worst dangerous This is illustrated by the Four Stages of Competence a classification posited in the by 1940s by psychologist Abraham Maslow You may have m Conscious incompetence You don t know something But you know that you re ignorant This is a relatively safe position to be in You probably don t care it s not something you need to know Or you know that you re ignorant and it is a source of frustration Conscious competence This is also a good state to be in You know something And you know that you know it To use this skill you have to make a conscious effort and concentrate Unconscious competence This is when your knowledge of a topic is so great that it has become second natu
76. keyl return it gt second second throws if called for non existing key const VALUE amp at2 const KEY2 amp key2 const const tBackMapIter it backmap find key2 1f it backmap end throw std out of range no key2 return it gt second gt second second Commentary As Pal wrote when thinking about test cases The real problem is cannot tell the expected behaviour of almost any of those In particular it is unclear what the code should do when one of the keys is a duplicate Pal also included the following comment along with his entry This is another of those poor quality examples where the context is too thin to show a solution So we re stuck with what ifs and pointing at mistakes in the code without really going out to the light I must agree with him at least in part In actual practice when people present code like this they often fail to explain what they re trying to do fortunately you can ask questions to elucidate the purpose of the code and point out corner cases that the original design missed This isn t always the case for example when maintaining a program after the original author has moved on but hopefully in these cases there are other ways to find out the code s desired behaviour However as the code critique is non interactive I will try to add a little more context to the problem in future This isn t a problem with the bug in the sample progra
77. knowledge that s hard to transfer by exposition that is only gained by experience and deep understanding m Expert This is the pinnacle of the learning tree There are very few experts They are authorities on a subject they know it completely and can use this skill interlinked with other skills They can teach others although they probably teach competents better than novices as there is less of a disconnect Experts have intuition so rather than needing rules they naturally see an answer even if they can t articulate why it s the best solution Why is the Dreyfus Model interesting It s a revealing framework to understand where you currently stand in the mastery of a topic and help determine where you need to get to Do you need to be an expert Most people are competent and this is satisfactory indeed a team of experts would be far too top heavy and probably dysfunctional It also illustrates how you should expect to be solving problems at each stage of your learning Are you looking for simple rules to apply hungrily gathering maxims to draw experience from or intuitively sensing answers How much of a big picture view do you have of the topic The Dreyfus model is also a very useful aid for teamwork If you know where a colleague sits on the notice expert spectrum you can better tailor your interaction with them It will help you learn how to work with other people should you give them some simple rules expla
78. led enabled public List lt String gt getAuths return auths public void setAuths List lt String gt auths this auths auths Then remove the lt servlet gt and lt servlet mapping gt elements from web xml so that it looks like Listing 6 lt xml version 1 0 encoding UTF 8 gt lt DOCTYPE web app PUBLIC Sun Microsystems Inc DTD Web Application 2 3 EN http java sun com dtd web app 2 3 dtd gt lt web app gt lt Default page to serve gt lt welcome file list gt lt welcome file gt UserManager html lt welcome file gt lt welcome file list gt lt web app gt lt html gt lt head gt lt meta http equiv content type content text html charset UTF 8 gt lt link type text css rel stylesheet href UserManager css gt lt title gt User Manager lt title gt lt script type text javascript language jJavascript src usermanager usermanager nocache js gt lt script gt lt head gt lt body gt lt hl gt User Manager lt h1 gt lt table align center gt lt tr gt lt td id gridContainer gt lt td gt lt tr gt lt table gt lt body gt lt html gt Again the lt servlet gt and lt servlet mapping gt elements are used by the example remote procedure call implementation and are therefore not needed UserManager html has a lot of HTML from the web application start project that we do not need so modify it so that it looks like Listi
79. ling a plugin to pull code from Bazaar repositories took about five minutes I poked around Hudson a bit more and found a setting to draw a chart of test results I can see why such a thing is useful in a team situation but Mango is one man project I build it and run the tests whenever I work on it Poking some more I found another setting that drew a chart of compiler warnings That s when I had a little revelation Continuous integration servers are useful to a group because they Il let you know and know quickly when the build has broken And that s true and it s areal benefit But it doesn t apply for a one man project When there s only you there s no one to integrate with If a test has failed it must be you by which I mean me who broke it and that must have happened in the last few minutes What CI servers can do for the one man project is remember Remember your test results Keeping track of build times Remember your compiler warnings Stuff you wouldn t yourself record unless you were an outrageously meticulous record keeper As it happened Mango had no compiler warnings in the build However I had another library that did Written in Java several years ago I hadn t had reason to work on it for quite some time Building with a modern Java compiler produced a slew of warnings which I d not had the inclination to fix Hooking up Hudson to build it within a few minutes I had a chart telling me exactly how
80. lt m at2 Vert lt lt endl cout lt lt std hex lt lt m atl Blue lt lt endl m erase2 Bleu cout lt lt size lt lt m size lt lt endl m erasel Blue cout lt lt size lt lt m size lt lt endl m erasel Red cout lt lt size lt lt m size lt lt endl cvu Critiques Balog Pal lt pasa lib hu gt I started wondering even before I got to the code The target is said to be a two way map and continues as it shall have two keys For me a two way map means a different beast a map where you can swap the roles of key and value and knowing either one can fetch the other What is described here I d name maybe a two key or alternative keyed map And I have used many of the first kind but nothing like this So the first thing I do is try design one such class in my head with essential functions and test cases Then compare that with the presented code The interface does not look hard we ll need some insertion with the keys and value and fetch by either key Possibly erase by either key too How many test cases will that need And here comes some explosion Like a zillion including repeated inserts and erases of the two key combinations The real problem is I cannot tell the expected behaviour of almost any of those Here I look at the code for some help to find indeed the basic functions are like imagined but neither the implementation nor the
81. m the user has provided though as they chose unique keys so we can resolve the bug here without necessarily needing to decide on the correct response to duplicate keys Many modern C environments provide extensive help with debugging usage of the standard library a good reason for preferring it in general to hand written containers so the first thing is to turn on the appropriate settings and see if additional light is thrown For example with g you might use D_GLIBCXX_ DEBUG with this option executed the program now generates the error message attempt to increment a singular iterator Or using the debugging runtime with Visual Studio for example with MDd you get an exception at the point of error the it in the loop inside erasel Either or even both of these techniques can greatly assist debugging this sort of trouble As Pal stated the problem is that modifying the map while iterating through it is dangerous and must be done using the iterator itself and taking care even so The debugging messages produced will make this easier to identify The easiest way to avoid the trouble in this case is simply to break out of the loop After all if we have found the key there s no point continuing to search the map anyway The Winner of CC 61 As Pal was the only entrant I am awarding him the prize However I have no compunction in doing so as his critique provided good coverage of the problems with the code
82. many warnings I had seventy together with breakdowns of warnings by type and class name hyperlinked into the source As I explored the warnings report some of them looked very simple to fix So I fixed them and committed the changes So Hudson rebuilt the code and sent me an email telling me it had That prompted me to look again at the Hudson build console where I saw the warnings graph had gone down a little Which prompted me to fix another warning You can probably fill in the rest See Figure 1 By remembering what had happened in previous builds and then telling me in an easy to understand way Hudson prompted me to fix a codebase that had languished for years The second spike on the chart is where having sorted out everything in the main code I turned on warnings in the test code count The psychological effect of that graph was really remarkable By having a record of the build warnings that didn t simply scroll off the top of the terminal and disappear I shamed myself ito fixing them while simultaneously providing a tool to help fix the problems and positive feedback as I did so I decided to make deliberate use of it When building my Arabica XML toolkit 3 Pve always used GCC s default warnings Recently I ve been exchanging emails with a chap called Ash who s using Arabica to provide XML support for the Flusspferd Javascript project Flusspferd builds at a higher warn
83. masks the characters that are entered There is check box for marking a user as enabled or disabled a list box to hold the authorities and buttons for finding and saving users and adding and removing authorities Creating the widgets is not enough They need to be arranged and displayed on a panel One way to do this is to use a Grid To keep the application readable and expressive create a buildGrid method private Grid buildGrid final Grid grid new Grid 5 5 Add widgets to grid return grid The Grid constructor takes the number of rows and columns in that order that are required The setWidget method is used to add widgets to the Grid It takes a row and column and the widget to add The widgets can be arranged any way you want but I ve decided to put the user name text box the Find and the Save buttons on the first row grid setWidget 0 0 new Label Username grid setWidget 0 1 usernameTextBox grid setWidget 0 2 findBtn grid setWidget 0 3 saveBtn You will notice that there is another type of widget here The Label widget allows you to put text into the grid as a widget so it s easier to customise with CSS You could use the setText method instead if you wanted to The first row is followed by the password text box on the next row grid setWidget 1 0 new Label Password grid setWidget 1 1 passwordTextBox then the enabled check box on the row after that grid setWidget 2 1
84. mbership types Basic personal membership Full personal membership Corporate membership What are you waiting for Student membership professionalism in programming WWW accu org MAR 2010 cvu 27 cvu Code Critique Competition 62 Set and collated by Roger Orr lease note that participation in this competition is open to all members whether novice or expert Readers are also encouraged to comment on published entries and to supply their own possible code samples for the competition in any common programming language to scc accu org A book prize is awarded to the winning entry am trying to write a simple two way map to allow items to be addressed by two different keys but I m getting some odd behaviour I ve written a simple test program and everything works fine except for the last line output expect the last size to be 1 but get 2 Can you help Last issue s code is shown in Listing 1 twowaymap h include lt map gt template lt typename T typename U gt class twoway map public typedef typename std map lt T U gt size type size type void insert const T amp keyl const T amp key2 const U amp value U amp p mapl keyl value map2 key2 amp p void erasel const T amp keyl1 if mapl find keyl mapl end for typename std map lt T U gt iterator it map2 begin it map2 end it if it gt second amp map1 keyl1 ma
85. name gt lt servlet class gt uk co marauder usermanager server UserServiceImpl lt servlet class gt lt servlet gt 22 cvu MAR 2010 public class UserServiceiImpl extends RemoteServiceServlet implements UserService Override public User find String username return null Override public void save User user The url at which the servlet will be accessed must also be configured using the lt servlet mapping gt element lt servlet mapping gt lt servlet name gt userManagerServlet lt servlet name gt lt url pattern gt usermanager user lt url pattern gt lt servlet mapping gt lt servlet mapping gt uses the name of the servlet as defined by lt servlet gt and specifies the url pattern with lt url pattern gt The first part of the url pattern before the slash is the relative to the server path to the web application and the second part after the slash is the name of the remote service and must be the same as specified in the RemoteServiceRelativePath annotation The remote service is now ready to call from the client To make a call to the remote service you first need to create an instance of the asynchronous interface You only need to do it once so make it a field of the UserManager public class UserManager implements EntryPoint private final UserServiceAsync userService GWT create UserService class A call can be made on an interface implementation instance just l
86. nd Paul McJones I sense this is an important book and a study group for it has recently been started at the C Next site 1 It s not an easy book it requires study and contemplation but such is the case for most of the valuable things in life This is one of the few books that contribute to putting our field on a firm mathematical scientific foundation so that software development one day may arise as a true engineering discipline To really get the full advantage of that book I think Ill ees be needing another book that I ve recently acquired enti _ Abstract Algebra by W E Deskins This appears to be i an accessible yet comprehensible introduction to the interesting field of abstract algebra a field that until recently I didn t know had any connection with generic programming but where it seems that this may be connected to taking generic programming to the next level That s two books I haven t yet read but where I ve started reading both and so far they are very promising Definitely desert island material Let s then move to a book I consider a classic one which I have read which is Multi Paradigm Design for C by Jim Coplien This is one of the first and few books that address the concept of multi paradigm software development in a systematic way Moreover it applies this to the C language Having read this book you ll hardly look at the language the same way again It s
87. nd makes an immense contribution to the ACCU As with so many others have been lucky enough to meet him at the ACCU conference Terje Sletteb I was honoured when Paul asked me if I could write an instalment in this series I ve felt I ve been quite out of the circulation both regarding C and ACCU for a while but some things are timeless and it would be timeless books and albums that you d want to bring with you on a desert island you d never know if or when you d be rescued Some others have wondered if we ve all ended up on the same island would it be a desert island then though and if that s the case I might borrow some of their books Knuth s The Art of Programming comes to mind so that I can bring some other ones instead The choices will be based partly on This is an important book for me and This is a book series I ve never got around to reading fully because it s so large or requires in depth study and contemplation Assuming I ve got a solar powered laptop with me and or have a remote hope of getting back to civilisation some time some of the books may then be computer related Such lists also tend to reflect one s current interests as when thinking of this I chose books that I d like to bring as if I was going to be stranded on that island tomorrow The first book I d like to bring is Elements of Programming by Alexander Stepanov a
88. ng 7 This leaves us with a basic host page that displays an appropriate title and a place holder gridContainer for our application that will be horizontally centred in the browser Finally remove all the web application starter project code from the UserManager class so that we just have the basic class public class UserManager implements EntryPoint public void onModuleLoad You now have a very basic GWT application with a place holder ready for the grid which will hold the widgets Run the application to make sure all is well Next add the widgets as shown in Listing 8 GWT widgets are a lot like Swing 7 widgets As you can see here there is a text box for the user name a password text box for the password and a text box for entering new rules The password text box is the same as a MAR 2010 evu 19 4cvu public class UserManager implements EntryPoint private final TextBox usernameTextBox new TextBox private final Button findBtn new Button Find private final Button saveBtn new Button Save private final TextBox passwordTextBox new PasswordTextBox private final CheckBox enabledChkBox new CheckBox Enabled private final ListBox authListBox new ListBox private final TextBox authTextBox new TextBox private final Button addAuthBtn new Button Add private final Button removeAuthBtn new Button Remove regular text box except it
89. nterface between the function or method P Il use function here to mean both and its caller When looking at a function signature usually at the prototype in a header file a caller can see what arguments need to be passed in However when looking at the function body the parameter list shows you what has been passed in If these two statements sound obvious then why do we so often neglect how these things are presented as if they are second class citizens in our code How often have you seen or written a function that takes some number of parameters where the parameter list is all on one line and spans more than a typical screen width sometimes several screen widths Often an attempt is made to rectify the situation by splitting the list over one or more lines sometimes even one parameter per line but by no means always Even then the tendency is to place the first parameter on the same line as the function name then try to line up the subsequent parameters with the first Something like listing 6 Does this look familiar I don t know about you but even though it might look like an extreme example I see this sort of code all the time And remember this is where someone has made an attempt to split across lines and use alignment Just today I saw an example on my current project of a function signature that was 239 characters wide and that was by no means the worst case in the project rocket science or brain surgery
90. nts UserService private final UserManager mgr Override public User find String username return getUserMgr load username Override public void save User user getUserMgr save user returned and handled by the client if the user cannot be found To save a User object just pass it to the save method If you run the application and try to save a user you will see that it is serialised to the database successfully However if you try to find that user again you will receive an error The call failed on the server see server log for details If you look at the output in the Eclipse console window or equivalent you will see the following exception message com google gwt user client rpc SerializationException Type org hibernate collection PersistentBag was not included in the set of types which can be serialized by this SerializationPolicy or its Class object could not be loaded For security purposes this type will not be serialized This is due to the way Hibernate handles retrieving collections Instead of putting the items into an ArrayList lt String gt which GWT knows how to serialise via RPC it puts them into its own class type org hibernate collection PersistentBag which GWT does not know how to serialise even though PersistentBag implements the need to know at compile time how an interface is implemented GWT needs to know about the complete hierarchy if itis going to be
91. o push our automated build a little bit further For various reasons Our environment is awkward Putting a release up into the test servers is complex and still involves a certain amount d of time and a degree of manual intervention unen there S only ou there s no one you to integrate with Consequently it isn t happening as often as it should We are in a quieter period at the moment and we re managing but when things hot up again it s going to be a problem What we would like to do is finish automating the process and have our CI server build and deploy nightly into our test environment With that complete we re going to try and kick off the GUI testing scripts as well Our testers can spend more time with their feet on the desk drinking tea while the developers can be secure that yesterday s work does actually work It s fallen to me to make this happen One of the things I needed to do first was spent a bit of time fiddling with the build server CruiseControl while a sound piece of kit doesn t however lend itself to easy fiddling It s driven by configuration files and to pick up changes you need to bounce the server If you make a mistake in the configuration it s not necessarily obvious why and that s just a faff and a time consuming one By coincidence as I started this work several people on accu general had been discussing the Hudson build server One thing that stuck in my mind was that Hu
92. object and initialises it with the user name password and enabled flag from the user name text box the password text box and the enabled check box It then iterates through all the authorities in the authorities list box and adds each one to the user Finally it is passes the User object to the saveUser method which we have not written yet GWT only implements a restricted subset of the Java API so any action that uses something outside of that subset such as writing to a database must be carried out on the server via an RPC call Making an RPC call is the equivalent to making a method call to the server and is actually quite easy to do with GWT First we need a Service interface which defines the methods we want to be able to call on the server The interface must extend GWT s RemoteService interface RemoteServiceRelativePath user public interface UserService extends RemoteService User find String username void save User user MAR 2010 evu 21 4cvu private void setupButtons findBtn addClickHandler new ClickHandler Override public void onClick ClickEvent event final String username usernameTextBox getText findUser username le saveBtn addClickHandler new ClickHandler Override public void onClick ClickEvent event final User user new User usernameTextBox getText passwordTextBox getText enabledChkBox getValue for int i 0 1 lt auth
93. oming a proficient programmer is tougher on these platforms than other platforms However the effort is worth it According to this book the Unix way of things consists of up to three layers 1 The UI layer which in turn sits on top of 2 The application layer which sits on top of 3 The small programs layer which implements the guts of the system This means as a user you can opt to use a GUI or the command line schell script to automate your intentions This also means as a programmer you can change any of the three layers without having to change the other two layers for example if your GUI falls out of favour you can replace the UI layer with new code The Three Systems rule is covered here The First System gets built and either dies or it gets developed into the Second System with the knowledge that it will get replaced by the Third final System As a semi final recommendation here are the key tenets stated by this book m Small is beautiful Make each program do one thing well Build a prototype as soon as possible Choose portability over efficiency Store data in flat text files Use software leverage to your advantage Use shell scripts to increase leverage and portability m Avoid captive user interfaces m Make every program a filter Finally this book is an engaging read that should be read by all Linux Unix software developers Concurrent Programming on Concurrent Programmin Windows on W dow
94. option i cflags regex constants icase expbuf assign argv 0 cflags catch std exception amp ex fprintf stderr Error s n ex what exit 1 return process expbuf enum option type ECMAScript 0x01 ie icase 0x0100 a template lt class charT class traits regex traits lt charT gt gt class basic regex sees typedef option _ type flag type f basic regex amp assign const basic regex that basic regex amp assign const charT ptr flag type f regex_constants ECMAScript basic regex amp assign const charT ptr size t len flag type f regex _constants ECMAScript template lt class s traits class A gt basic regex amp assign const basic string lt charT s traits A gt amp s flag type f regex _ constants ECMAScript template lt class InputIterator gt basic regex amp assign InputIterator first InputIterator last flag type f regex constants ECMAScript E typedef basic regex lt char gt regex template lt class charT class traits gt bool regex search const charT s const basic regex lt charT traits gt amp re regex constants match flag type f regex constants match default Paul Grenyer strands Terje Sletteb with nothing but a few books and some music for company though he has been rather quiet of late Terje exploded onto accu general only a few years ago Terje always has a lot to say a
95. or the dash character When cat is running and it reaches the parameter it copies its own input stdin to its output stdout before going on to process any remaining parameters What is the use of that If you want to inject data into a pipeline this is where the cat command begins to be useful ps x tee ps output txt awk print 5 4 sort cat heading txt 4cvu Daire Stockdale shares a recent source of inspiration http www realtimeworlds com for sharing with us inspiration from a a seemingly unlikely source a book about evolution The idea that complicated systems can be formed from simple rules is beautiful and inspirational T hanks to Daire Stockdale a senior software engineer working for I m not sure I have the time or wordcraft to write a piece but I did find reading Dawkins latest book The greatest to be almost an epiphany I suspect that similar to many reading this list biology was my least favourite science I preferred maths and physics and of course I thought I understood evolution However Dawkins book highlights the elegant simplicity of our world in such a beautiful way and I found it really appealed to my programmer s heart Whereas previously I had understood evolution to mean a process that was fantastically complex but which worked due to the sheer timescale available to it a brute force algorithm searching for best fits he explains that in fact it is even sim
96. p2 erase it gt first mapl1 erase keyl1 void erase2 const T amp key2 if map2 find key2 map2 end for typename std map lt T U gt iterator it mapl begin it mapl end it if amp it gt second map2 key2 Roger has been programming for over 20 years most recently in C and Java for various investment banks in _ Canary Wharf and the City He joined ACCU in 1999 and the BSI C panel in 2002 He may be contacted at rogero howzatt demon co uk 28 cvu MAR 2010 mapl erase it gt first map2 erase key2 U amp atl const T amp keyl1 return mapl1 keyl1 U amp at2 const T amp key2 return map2 key2 size type size const return mapl size private std map lt T U gt map1 std map lt T U gt map2 test cpp include twowaymap h include lt string gt include lt iostream gt struct colour colour colour int r int g int b rgb r lt lt 16 g lt lt 8 b operator int return rgb int rgb using std cout using std endl int main twoway map lt std string colour gt m m insert Red Rouge colour 255 0 0 m insert Green Vert colour 0 255 0 m insert Blue Bleu colour 0 0 255 cout lt lt size lt lt m size lt lt endl cout lt lt std hex lt lt m atl Red lt lt endl cout lt lt std hex lt
97. pler and from the moment the process begins it necessarily and quite rapidly produces results More About Bash continued This command line lists processes and sends a copy of that data to stdout and tops output txt awk s input stdin is tied to tee s output stdout which prints the 5th and 4th text fields of the ps output Finally cat is used to send a heading to stdout closely followed by stdin to stdout For instance if I wasn t sure what ps was outputting I could try ps x tee ps output txt awk print 5 4 sort Once the pipeline has finished executing looking atps output txt might yield clues regarding the pipeline s behaviour m References 1 Ian Bruntlett Interpreting Custom Unix Shell Scripts in CVu 21 4 September 2009 2 Ian Bruntlett Beyond Pipelining Programmes in Linux in CVu 21 5 November 2009 3 Tony Stubblebine Regular Expression Pocket Reference O Reilly This book refers to Mastering Regular Expressions by Jeffrey Friedl also from O Reilly 4 D J Barrett Linux Pocket Guide O Reilly Bibliography Mike Gancarz Linuz and the Unix Philosophy Digital Press Arnold Robbins sed amp awk Pocket Reference O Reilly a process that Show on Earth explaining the inner details of evolution WAS fantastically complex but which worked due to the sheer timescale available to it He explains far better then I can here how the apparent complexit
98. porary file grep would terminate OK and the resulting temporary file sent as input to the more command In Unix however grep and more are started as a pipeline of programmes How does this work Well both grep and more are started together with a pipeline connecting the output stdout of grep to the input stdin of more It s pretty easy to pick up all the DOS commands nix commands are documented in Big Fat Books from O Reilly and many of the commands seem trivial However in nix the sum of the combined parts is greater than the whole See my review of Linux and the Unix Philosophy a book that hammers home the tenet that all data should be text based however I still believe that binary files are important So if you re looking at a nix shell script and you re wondering what the individual commands do you can either buy a book or use the inbuilt help Both have their values My copy of the Linux Pocket Guide has got lots of notes in the margins Despite liking the dead tree version I think one day I will mainly use the on line help Quite often people are encouraged to read the man pages The man command short for manual searches a database On Rutherford PC running Ubuntu 9 10 that database is scattered into folders held inside usr share man For example running man man gives you 600 lines of text that describe man and lists its command line options It handles paging so you ll never need to type man wi
99. rManager gt lt source path client gt lt module gt simple the application is demonstrating two of the most important features of GWT m The ability to write a web application front end in Java E Remote procedure calls Let s take a look at the project structure As you can see from Figure 4 GWT projects have a fairly normal Eclipse project structure with a few extras The extras are the GWT SDK which consists of the two JARs needed to write and compile Java code and the war directory which provides a deployable structure for the web application When the application is ready for deployment this directory can be zipped into a war file and deployed to a servlet container such as Apache Tomcat 4 GWT project structure is explained in detail in the Organising Projects development guide 5 on the GWT website I have included some extracts below to give an overview Individual units of GWT configuration are called modules A module bundles together all the configuration settings that your GWT project needs m Inherited modules m An entry point application class name these are optional although any module referred to in HTML must have at least one entry point class specified Source path entries Public path entries Deferred binding rules including property providers and class generators Modules are defined in XML and placed into your project s package hierarchy Modules may appear in any package in your classp
100. rain and change the way I worked on my individual projects W 1 Building a Feature with Continuous Integration http martinfowler com articles continuousIntegration html BuildingA Feature WithContinuousIntegration 2 Mango Java library of iterators algorithms and functions http www jezuk co uk mango 3 Arabica an XML and HTML toolkit written in C http www jezuk co uk arabica 4 Flusspferd Javascript bindings for C http flusspferd org a fs i f ae sN WWW ACCU ORG l PROFESSIONALISM IN PROGRAMMING while you care about read Bcvu gs amp overload 7m do it E d i j because good code matters ACCU ih F t r a o r X rs MAR 2010 evu 9 cvu Code Formatting in C Phil Nash explains why format counts ode formatting or layout is one of the most religious areas of software development With so many bloody battles fought and lost most developers learned long ago to avoid the matter altogether They tend to do this by making consistency the only rule that matters When in Rome do as the romans do After all everyone knows that it s all subjective and doesn t actually matter Or does it I m going to present a couple of views that I hope will lead you looking at the matter once again Some of them a little cliched Some a little more novel First one of the cliches code is written for humans to read
101. re You are no longer aware that you are using your expertise Most adults for example can consider walking and balance as an unconscious competence we just do it without a second thought Unconscious incompetence This is the dangerous place to be You don t know that you don t know something You are ignorant of your ignorance Indeed it is very possible that you think you understand the subject but don t appreciate how very wrong you are It is a blind spot in your knowledge So be very careful when claiming competence in any subject let alone any level of expertise Psychologists biologists and other similar evil geniuses have studied the human brain for years and have formulated many models of brain behaviour and models of learning There is an overwhelming quantity of research on the subject some quite contradictory Understanding at least at a basic level how the brain works and some of its characteristics will help us work out how to learn most effectively The left brain right brain split We hear a lot about the left brain and the right brain These terms have entered pop culture and you are as likely to hear them discussed by artists and CEOs as by psychologists It comes from research pioneered in the 1970s by Roger W Sperry who coined the left right brain terminology discovering that our mental activity is split between the two hemispheres of the brain either side controlling a different mod
102. re still not at a level where you can comprehend the bigger picture The beginner can t focus out irrelevant details as far as they re concerned everything and anything could be important to the problem at hand Beginners rapidly gain explicit knowledge the kind of factual knowledge than can be easily written down and articulated Competent This stage sees you with a mental model of the problem domain you ve mapped the knowledge base and have begun to associate parts and understand the relative importance of different aspects This big picture view allows you to approach unknown problems and plan methodical routes into those problems rather than diving in and hoping rules will get you to a solution This is a good place to be m Proficient people move beyond competency They have a much better understanding of the big picture and are frustrated with the simplifications that the novice needed They can correct previous errors and reflect on their experiences to work better in the future At this point you can also learn from other s experiences and assimilate them into your body of understanding Proficient people can interpret maxims as opposed to simplistic rules and apply them to a problem e g they know how and when to apply design patterns Now it is easy to identify and focus only on the issues that really matter confidently ignoring irrelevant details Here we see the person has gained significant tacit knowledge
103. rg Our advertising rates are very reasonable and we offer advertising discounts for corporate members 2 cvu MAR 2010 team is on hand if you need help or have any queries COPYRIGHTS AND TRADE MARKS Some articles and other contributions use terms that are either registered trade marks or claimed as such The use of such terms is not intended to support nor disparage any trade mark claim On request we will withdraw all references to a specific trade mark and its owner By default the copyright of all material published by ACCU is the exclusive property of the author By submitting material to ACCU for publication an author is by default assumed to have granted ACCU the right to publish and republish that material in any medium as they see fit An author of an article or column not a letter or a review of software or a book may explicitly offer single first serial publication rights and thereby retain all other rights Except for licences granted to 1 Corporate Members to copy solely for internal distribution 2 members to copy source code for use on their own computers no material can be copied from C Vu without written permission from the copyright holder Professionalism in Programming 60 Live to Love to Learn Part 2 Pete Goodliffe continues his journey of self improvement Learning is like rowing upstream not to advance is to drop back Confucius improvement This is an unrepentant explor
104. rganisations Reasonable rates Flexible options Discounts available to corporate members Contact ads accu org for info 36 cvu MAR 2010 The 22nd AGM Notice is hereby given that the 22nd Annual General Meeting of The C Users Group UK publicly known as ACCU will be held at 13 00 on Saturday 17th April 2010 at the Oxford Barcelo Hotel formerly the Oxford Paramount Hotel Godstow Road Oxford OX2 8AL United Kingdom Current Agenda 1 Apologies for absence Minutes of the 21st Annual General Meeting Annual reports of the officers Accounts for the year ending 31st December 2009 Election of Auditor Election of Officers and Committee Other motions for which notice has been given Any other Annual General Meeting Business to be notified to the Chair prior to the commencement of the Meeting The attention of attendees under a Corporate Membership is drawn to Rule 7 8 of the Constitution Voting by Corporate bodies is limited to a maximum of four individuals from that body The identities of Corporate voting and non voting individuals must be made known to the Chair before commencing the business of the Meeting All individuals present under a Corporate Membership have speaking rights Also all members should note rules 7 5 Notices of Motion duly proposed and seconded must be lodged with the Secretary at least 14 days prior to the General Meeting and 7 6 Nominations for Officers and Committ
105. s By Joe Duffy published by b Addison Wesley ISBN 978 D 0321434821 n This is one of the thicker books on my bookshelf with a whopping 958 pages and with good reason it is a comprehensive guide to both the Win32 and NET multithreading APIs on Windows As well as explaining in detail how to use the various functions and classes Joe goes into some detail explining the basics of concurrency and why things are done a particular way This covers everything from the basics of the x86 memory model and how that affects the visibility and synchronization of data between processors to the thread scheduling model for Windows There is in depth coverage of all the synchronization primitives as well as the Windows thread pool support and asynchronous I O The comprehensive coverage of the NET Parallel Extensions has been relegated to an appendix as the library was only available as a preview at time of writing but there s more than enough material in the main part of the book on the main NET library Joe hasn t just covered the APIs either there s a good discussion of various programming models for concurrency such as data parallelism and task parallelism a section on lock free programming as well as sample implementations of data structures that are safe for concurrent access from multiple threads This is an indispensible book for anyone wishing to use the native APIs when writing multithreaded programming on
106. s and interests us surely a prerequisite for effective learning But often such high specialisation is detrimental to your ability to learn in general It ingrains a lack of curiosity for other disciplines or any appreciation of the wider human experience However it is when disciplines collide that we often see the the most exquisite insights consider for example how Alexander s architectural work illuminated the field of software design 1 Learning is hard When an infant learns the world is new and exciting as they coast through it they just absorb stuff After a certain point the things you have to learn become less interesting Adults force you to learn stuff It involves effort Effort which you could expend on other tasks like playing with your friends or your toys Then you re given homework and learning starts to take over your precious free time It feels like hard work It is hard work Learning 1s hard That hard work will though be rewarded But it s easy to resent learning as a tedious chore that stands between us and fun or ability Many people s early school experience of learning still colours their adult life approach to learning even if they don t realise it How often have you balanced the reward of learning something against the effort involved How often has the initial learning effort put you off learning something new Are you now automatically programmed to avoid areas you kno
107. several words horizontally and vertically in at each fixation We can add to that another counter intuitive nugget from the speed reading world Good speed readers don t necessarily scan left to right then down the page assuming a western reading context but may scan in different directions according to different strategies e g scanning down the page then back to the top for the next column even if they then have to mentally reassemble back into the original word order I never got to this stage None of this addresses the question of whether this is even worth looking at Are we trying to solve a problem that doesn t exist We re constantly warned against premature optimisation but can that apply to our approach to code layout too Actually we have touched on one relevant principle already I ll highlight it again here The smooth flowing word by word reading experience that we perceive is an illusion Why is this relevant Well for one it tells us that what we think is happening is not necessarily what is actually happening A lot of processing is occurring before the material we are reading is even presented to us consciously With practice we can get better at reading unoptimised material so much so that we are unaware of it That doesn t mean the processing isn t happening Processing has a cost associated with it It tires us in particular it tires parts of the brain that we tend to use for other programmin
108. sorts When it arrives freshly formatted the human brain rapidly absorbs information and develops skills across a wide range of experiences It s a remarkable device both intricate and powerful and we need to learn how to best use it Unfortunately it doesn t come with a User s Manual Even if it did most men wouldn t read it anyway Our learning is often too narrowly focused Infants absorb information in many disciplines rapidly And simultaneously They don t know that they re simply not supposed to But all too soon our training starts we re introduced to the thought police Or rather at school we hop on board the academic train and our incredible generalised learning capability is slowly frittered away At primary school we are taught a range of topics At secondary school these topics are formalised and compartmentalised somewhat As we progress through the academic system we cut out certain topics and concentrate on those that suit us best because of interest or aptitude At UK GCSE level we narrow the focus to about 8 subjects We progress to A Level and narrow that focus to 3 or 4 subjects Then we progress to university level where we focus on a single subject This increasing focus in learning is useful in that it allows us time to become highly proficient in one area and to devote time to practise the specific skills required to master that subject It also allows us to chose a single topic that excite
109. t width 200 gwt Grid border 1px solid black public class Grid extends com google gwt user client ui Grid public Grid int rows int columns super rows columns this setStyleName gwt Grid for int x 0 x lt columns x for int y 0 y lt rows ty this getCellFormatter setAlignment y x HasAlignment ALIGN LEFT HasAlignment ALIGN TOP Appendix A Installing GWT 2 0 Eclipse plugin Although Eclipse 10 is not required for working with GWT it can make development much easier If you do not want to use Eclipse the SDK can be downloaded by itself and a supplied tool used to generate projects from the command line The GWT plugin is available for versions 3 5 Galileo 3 4 Ganymede and 3 3 Europa of Eclipse More information is available from the GWT Plugin 11 download page The GWT plugin is best installed into a fresh install of Eclipse I am currently using Galileo for Java EE developers eclipse jee galileo SR1 win32 but the plugin works just as well with the standard version The GWT plugin has a dependency on Eclipse s Web Standard Tools WST which if not already installed can be installed as follows 1 Go to the Help menu and select Install new software 2 Ifit isn t already present manually add the appropriate update url http download eclipse org releases galileo 3 Then expand Web XML and Java EE Development from the list and select Eclipse We
110. t tr gt lt td id nameFieldContainer gt lt td gt lt td id sendButtonContainer gt lt td gt lt tr gt lt table gt lt body gt lt html gt MAR 2010 evu 17 4cvu public class UserManager implements EntryPoint public void onModuleLoad final Button sendButton new Button Send final TextBox nameField new TextBox nameField setText GWT User sendButton addStyleName sendButton RootPanel get nameFieldContainer add nameField RootPanel get sendButtonContainer add sendButton m Specifies the body of the HTML tag including two place holders for GWT functionality nameFieldContainer and sendButtonContainer The td tags include an id attribute associated with them This attribute is accessible through the DOM class You can easily attach widgets using the method RootPanel get Entry point classes A module entry point is any class that is assignable to EntryPoint and that can be constructed without parameters When a module is loaded every entry point class is instantiated and its EntryPoint onModuleLoad method is called Part of the UserManager entry point class UserManager java is shown in Listing 3 Here a button and a text box widget are created and attached to the HTML host page via RootPanel get There is plenty more code in UserManager java which I have not shown It along with the code in GreetingService java GreetingServ
111. test suggests the solution The visible insert works with triplets good and we have the sneaky inserts with the atX functions that make no sense so look more like a bug Suppose not having that let s start with empty map and insert triplets a A 1 b B 2 After that what should happen on inserts a A 1 a A 2 a C 1 a B 1 b A 1 And after those issuing erase on any of the existing keys or on a non existing one Even without an extra insertion what erase shall do remove the whole triplet or let the other half pair linger The testing part just writes out the result without telling what is expected The just the last 1s bad is hardly enough information with the code that smells undefined behaviour with the pointer and iterator juggling The expected result of the second erase would be interesting but all we re told it is okay at executing there Trying to run it lands ina crash right at the first erase attempt Incrementing the iterator that was just invalidated by the erase Fixing that the output is 2 2 2 whether just by accident is to be seen So let s look the code for problems I start with the struct colour It is hardly meant seriously probably just dropped in to have something to drive the test but still it is better put it into shape m Its default ctor does not init the state Member rgb shall be initialised to something say 0 preferably in the init list The way
112. that aspect Whether that makes sense for your application is another matter I m not suggesting you lose the benefit of declaring variables closer to where they are used What I really want to illustrate is what happens if you add a bit of whitespace for alignment purposes See listing 4 Now most of us have probably seen code like this Maybe we already prefer such a style But quite a number of developers seem to be against it either actively they really dislike it or at least have concerns over the extra overhead of writing and maintaining in this style Well if you re one of that number please bear with me There is more to get out of this yet Also as we ll see I believe the big wins are actually in other areas that we re building up to So let s analyse the properties of his format for a moment Firstly we have three columns here The first column contains the types The second the names and the third the initially assigned values if any One of the potential problems here is that as each column 1s as wide as the longest field in that column the more columns we have the more horizontal space we ll end up using In C between templates and namespaces this can get out of control quickly As we ll come onto a bit more later if you have to scroll to take in a line you ll undermine any efforts to make things more readable Another problem is that it amplifies the objection over the writing and maintenance overhead
113. the remove button should only be enabled when an authority is selected in the authorities list box Create another method called setupAuthWidgets and start by setting the number of visible items for the list box and disabling both the buttons private void setupAuthWidgets authListBox setVisibleItemCount 5 removeAuthBtn setEnabled false addAuthBtn setEnabled false Call it after adding the grid to the panel public void onModuleLoad RootPanel get gridContainer add buildGrid setupAuthWidgets To detect whether there is text or not in the authorities text box we need to add a change handler authTextBox addChangeHandler new ChangeHandler Override public void onChange ChangeEvent event final TextBox tb TextBox event getSource addAuthBtn setEnabled tb getText length gt 0 Put this change handler in the setupAuthWidgets method When the contents of the authorities text box changes the change handler s onChange method is called Its ChangeEvent parameter includes a reference to the widget that has changed which is accessible via the getSource method which returns object so must be cast to the cvu appropriate type Getting the text from the text box and checking its length is then used to enable and disable the authorities add button via its setEnabled method We also need a change handler to enable and disable the authorities remove button
114. updateUser method for display in the interface If it is not found null is passed back and the user is informed via a message box that the user could not be found The updateUser method looks like this private void updateUser User newUser usernameTextBox setText newUser getUsername passwordTextBox setText newUser getPassword enabledChkBox setValue newUser isEnabled authTextBox setText authListBox clear for String s newUser getAuths authListBox insertItem s 1 As you can see it takes the user name password and enabled flag from the User object and uses them to set the text or value in the appropriate widget It then clears the authorities list box and the inserts the authorities from the User object The saveUser method is similar Listing 12 Again the onFailure method reports failure to the user The remote service save method return type is void there is nothing returned However the onSuccess method must still be implemented to indicate when the method returns Its single parameter is therefore of type Void If the User object is successfully saved the clear method is called to clear all the widgets and a message box is displayed to the user indicating success The clear method is implemented as follows private void clear usernameTextBox setText passwordTextBox setText enabledChkBox setValue false authTextBox setText authListBox clear
115. utes That s probably as much increase in throughput as 1s worth doing at this stage since the time cost of the latency is now much greater than that of the throughput So how would we reduce the latency Well we could try and reduce the distance travelled take out all the bends in the highway and have it made into a straight line between the start and the finish That s probably a little excessive so the most obvious way to reduce the latency is to speed up the cars So let s assume that there are no highway patrols and no speed cameras so we can double the speed That means that it ALAN LENTON Alan is a programmer a sociologist a games designer a wargamer writer of a weekly tech news and analysis column and an ocassional writer of short stories see http www ibgames com alan crystalfalls index html if you like horror None of these skills seem to be appreciated by putative employers So in the next instalment I promise we ll look at some very practical techniques to improve our learning capabilities 1 Design Patterns Elements of Reusable Object Oriented Software Gamme Helm Johnson and Vlissides Addison Wesley ISBN 0201633612 and A Pattern Language Towns Buildings Construction Alexander ISBN 0195019199 Lateral specialization in the surgically separated hemispheres R W Sperry in Neurosciences Third Study Program F Schmitt and F Worden Eds Cambridge MIT Press 3 5 19 1974
116. vicelImpl java UserManager html A host HTML page that loads the UserManager application A static style sheet that styles the UserManager application war usermanager The UserManager module directory where the GWT compiler writes output and files on the public path are copied armes __ Alnorpubic resources ve here see the servet specication tor more detal arWEBINFcasses ava compiea class tles ive here to implement server sie funcionaiy barmwesaneno Ary ibrary dependencies the servor code needs gohere war WEB INF lib 18 cvu MAR 2010 gwt servlet jar This GWT JAR is needed for RPC support cvu public class User implements IsSerializable private String username private String password private boolean enabled private List lt String gt auths new ArrayList lt String gt SuppressWarnings unused private User public User String username String password boolean enabled this username username this password password this enabled enabled public void addAuth String auth auths add auth public String getUsername return username public void setUsername String username this username username public String getPassword return password public void setPassword String password this password password public boolean isEnabled return enabled public void setEnabled boolean enabled this enab
117. w nothing about because it is uncomfortable to appear ignorant Have your past experiences coloured the way you approach learning We must learn how to learn Many people were spoon fed information in school and told not to criticise This instils a bad attitude to learning where it is something someone gives you or that a teacher does to you Learning is actually a personal process that you have to take individual responsibility for Do you take personal responsibility for your own learning Don t blithely accept what you re told Keep your brain engaged It s dangerously easy to fall into the trap of believing what you re reading or being told is the gospel truth rather than something that should be evaluated m How many people read things on the internet and presume that they are true Wikipedia has a genuine air of authority yet contains many remarkable mis truths Some of the tubes of the internet are rather grimy m How many people read things in their newspaper and unquestioningly presume that they are correct True there are lunatics out there on the web but paid journalists wouldn t make things up would they Wrong there are plenty of lunatics in the media too If you believed everything you read in the newspaper then you wouldn t eat or drink anything for fear that it would given you an incurable disease m If it s in a textbook written by an academic peer reviewed and recommended by a prestigious un
118. when I disagree with parts of this book that either the disagreement is caused by 1 misunderstanding some of the text or 2 where I would opt for optimisation the book would opt Given that I only can bring one more book although it s not really a novel I d like to choose From Science to God If I can t bring that one 1t would be some other spiritual book such as Bhagavad Gita The Prophet or Jonathan Livingston Seagull It would be a difficult choice Two albums This is even tougher than the choice of books To be honest I don t have two or even one album that stands out to such a degree that they are obvious candidates to bring It s more the case of a series of albums that I d like to bring My taste in music is perhaps more mainstream than my choice of novels I guess it can be described as pop rock ambient Artists I appreciate include Celine Dion Sandra Cretu Enigma Deep Forest etc Once I start thinking about my CDs the choice becomes difficult For those long days at the island I d like to bring something that speaks to my heart Savage Garden s Affirmations is surprisingly good and can move you to tears Then there are instrumental masterpieces IMO like Delertum s Karma However given that I may be alone on the island I d like to bring something with a human voice Perhaps surprisingly I ve come to that I d like to bring Lene Marlin s Playing My Game and
119. when an item in the authorities list box is selected or no items are selected authListBox addChangeHandler new ChangeHandler Override public void onChange ChangeEvent event final ListBox 1b ListBox event getSource removeAuthBtn setEnabled lb getSelectedIndex 1 Put this change handler in the setupAuthWidgets method It works in the same way as the change handler for the text box except that the list box s getSelectedIndex method is used to determine if an item is selected If no item is selected it returns 1 To add authorities into the authorities list box you need to add a click handler to the authorities Add button addAuthBtn addClickHandler new ClickHandler Override public void onClick ClickEvent event authListBox insertItem authTextBox getText 1 When the button is clicked the onClick method is called The contents of the authorities text box is read and inserted into the authorities list box at position 1 which means new authorities are always inserted at the top of the list A click handler is also needed to remove items from the authorities list box removeAuthBtn addClickHandler new ClickHandler Override public void onClick ClickEvent event authListBox removeltem authListBox getSelectedIndex In this case when the Remove button is clicked and the onClick method called the index of the currently selected item is retrieved usin
120. whilst I decide on my first move E Figure 1 shows the distances of squares from O and Figure 2 shows coins and controlled squares after each round of a game heads O tails X 4 3 2 1 1 2 3 Coe eae ee ER RE ERED pi Pt TT pi Pt td PEE Oy 1 SaaS eee e ix SSS Pit eT tT PRR pt txt pi tt fot Te ee Ie x x x x ololo x x x x o o o o d XT eleloo Listing 1 is a struct representing a position listing 2 is measuring the distance between two positions listing 3 is calculating the scores struct position size t rank size t file position position size t rank size t file bool operator const position amp x const position position position position size t rank size t file rank rank file file bool position operator const position amp x const return rank x rank amp amp file x file MAR 2010 cvu 13 cvu The Baron s student acquaintance plays the game ecall that the Baron s latest game involved taking turns to select cards from the set AV 29 3V AA 2A 3A A 2 3 and trying to construct tricks of three cards with either the same suit or face value The Baron s opponent is the first to select a card and has the advantage that three cards all differing in both suit and face value are a winning trick provided they include the first card selected The Baron balances this advantage
121. with the fact that he is also considered the winner if neither he nor his opponent can build a winning trick before the cards are exhausted Upon hearing the rules I immediately exclaimed that the game is isomorphic to the children s game of tic tac toe as can readily be seen by properly laying out the cards upon the table Specifically the first card chosen by the Baron s opponent should be surrounded by the remaining cards such that each row is formed from one suit and each column from one value For example if the first card is 34 we could lay out the cards as follows Ate 2 oe AA 2h AY 2V Here the Baron s winning tricks are the rows and columns and his opponent s the rows columns and diagonals A Game of Strategy continued size t abs diff size t x size t y return x gt y x y y x size t distance const position amp x const position amp y const size t rank dist abs diff x rank y rank const size t file dist abs diff x file y file return std max rank dist file dist size t shortest const position amp x const std vector lt position gt amp moves size t best 8 std vector lt position gt const_iterator first moves begin std vector lt position gt const_ iterator last moves end 14 evu MAR 2010 Now when the Baron selects a card we shall place an X in the gap and for his opponent an O Doing so an example of play might be Ax
122. x File Edit View History Bookmarks Yahoo Tools Help 2 Most Visited Getting Started gt Latest Headlines User Manager Username Password C Enabled Authorites GY http locathost 8888 UserManager htmI gwt codesvr 192 168 106 1 9997 7 Live Search Finally There is plenty more you would want to do to this web application such as disable all widgets when the find is in progress provide a list of users to choose from instead of relying on the find provide a list of authorities and prevent duplicates etc but implementing these is not necessary to demonstrate creating a GWT application with RPC and Hibernate The Google Web Toolkit is a far more powerful and elegant tool for creating web application front ends than any of the JSP based libraries used by most Here I have demonstrated just how easy it is as well as demonstrating how to avoid some of the pitfalls GWT can do a lot more than I have shown here and I hope to Done 24 cvu MAR 2010 demonstrate further features in future articles W cvu h1 font size 2em font weight bold text align center gwt Label font size 12pt gwt Button font size 12pt width 80 gwt TextBox font size 12pt width 200 gwt PasswordTextBox font size 12pt width 200 gwt listBox font size 12pt width 200 gwt CheckBox font size 12p
123. xations At each fixation the eyes transmit a chunk of information to the brain The size and content of each chunk varies and is one of the areas that a speed reader will exercise attempting to take in more information at each fixation to avoid wasting too much seek time An average untrained in the speed reading sense reader will take in about 2 4 words per fixation For longer words this will decrease and if the words are unfamiliar may drop below the one word per fixation level int main int argc char argv printf hello world n cvu Following from this is the insight that as well as several words along the same line being taken in in a single fixation multiple lines may be taken in But that s crazy talk When you re reading you don t read the lines above and below do you unless you re regressing which is a bad habit that speed readers try to overcome as soon as possible Well speed readers will push the envelope here but even for the rest of us we will still be taking in more information than we are consciously reading The smooth flowing word by word reading experience that we perceive is an illusion There is actually a disconnect between the information being captured by the eyes transmitted to the brain assembled and interpreted and the perception of words flowing through our conscious minds We re in danger of getting too deep here Let s stick with the knowledge that we can take
124. y of nature really is emergent from a few simple rules and that its not so hard to fashion the changes we see around us I think programmers will really appreciate and get these sections of the book more than most After reading the book I can t see cats and dogs without appreciating just how easy it is for natural selection to morph between them Also when he talks of the impossibility of knowing what a given DNA sequence produces without actually growing it 1 I was reminded of Turing program stopping problems I also found myself admiring the painstaking attention to detail gone to in by experimental biologists in proving through example evolution at work Even if you think you understand evolution this book will probably surprise and enlighten you After reading my copy I have gone and bought some more for friends 1 My terminology I m not sure what this process might actually be called JOIN ACCU You ve read the magazine Now join the association dedicated to improving your coding skills ACCU is a worldwide non profit organisation run by programmers for programmers Join ACCU to receive our bi monthly publications Vu and Overload You ll also get massive discounts at the ACCU developers conference access to mentored developers projects discussion forums and the chance to participate in the organisation How to join Go to Www accu org and click on Join ACCU Me
125. ypename KEY2 KEY gt class twokey map private typedef std map lt KEY std pair lt KEY2 VALUE gt gt tMap typedef typename tMap const_iterator tMapIiter a typedef std map lt KEY2 KEY gt tBackMap typedef typename tBackMap const iterator tBackMapIter tMap map main holder of value auxillary info is the second key tBackMap backmap links the other key to the main holder private helpers to access element that is expected to be there tMapIter findi const KEY amp key const const tMapIter res map find key if res map end throw std out of range no keyl return res tBackMapIter find2 const KEY2 amp key2 const const tBackMapIter res backmap find key2 if res backmap end throw std out of range no key2 return res 30 cvu MAR 2010 public overwrites any existing association on either key void insert const KEY amp key const KEY2 amp key2 const VALUE amp value erasel key erase2 key2 backmap key2 key map key std make pair key2 value throws if called for non existing key const VALUE amp atl const KEY amp key const return findi key gt second second throws if called for non existing key const VALUE amp at2 const KEY2 amp key2 const return atl find2 key2 gt second fe no op if called for non existing key void erasel const KEY amp key const tMapIter it

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