Simple Logo ("Slogo") CS32 Assignment 3
Contents
1. Plan this project in stages It may be helpful to build complete individual components before attempting to integrate them For the parser interpreter be sure that you can handle simple logo commands such as the math operations and turtle motion commands You could also write a test driver for the turtle graphics interface Then you should concentrate on getting Simple Logo to work with input from a terminal before you start to worry about getting file input output func tional This program is not an all or nothing project you can and should get smaller components working before you put everything together That s fantastic It sounds so easy How does it work and is it legal The Simple Logo language has been restrictively defined to make writing it a reasonable project In particular the limited definition should make it easier to do parsing and error checking Slogo 3 Writing the parser interpreter The logo interpreter could consists of a parser which breaks up the command and argu ments into tokens and decides what action to take and a command interpreter which executes the parsed command The parser will need to read in a line at a time from either a terminal or a file and divide the input string into tokens Given the restricted definition of the language there should only be one command per line and the command should be in prefix form with the command name at the beginning of the input string There can also be lines2. an interpreter for the language you once knew and loved so well Logo truly is the Frosted Mini Wheats of cs 32 projects the adult in you must carefully engineer a significant piece of soft Slogo ware then the kid in you gets to make saucy pictures in Logo Unfortunately you can t play until you re done so get designing get hacking and get done It s based on a simple concept yet the possibilities are limitless Logo is a computer programming language designed for use by learners in fact it is used in CS4 for the first programming assignment The user friendly interpreted language based on LISP was designed with the low floor high ceiling principle in mind that is the designers of Logo intended for the language to allow novice programmers to get started quickly with writing programs but also wanted the language to be powerful and extensive for more advanced users In the early days Logo was used to control a simple robot called a turtle Users could issue commands such as FORWARD 50 to make the turtle advance 50 steps or RIGHT 90 to make it turn ninety degrees The turtle robot carried a pen so users could produce drawings on paper such as the one on the previous page by controlling the turtle and its pen The turtle which has since moved on screen has become one of the most familiar and important parts of the Logo language Children who were using the computer for the first time could relate to talking to
3. one handin for each pair you should also hand in a revised copy of your object diagram which reflects your final design You should also create a README file which describes your overall design each file in your project any known bugs or bells and whis tles and anything else you want us to know Note that both of the designs you hand in will count as a substantial part of your grade You are responsible for printing out source code and the README labelling the separate files and putting both your names and account numbers on them before Spm on the day after your handin This should give you ample time to print out your code Please put the printouts in a sensible order with the README first Please hand in only the README and the source code and not any extraneous pages cover pages etc printout by the CIS printer Slogo 5 Appendix A Simple Logo Language Details This document contains a description of the Simple Logo language including supported commands their usage and effects Language Structure Slogo e A word beginning with a colon is a variable e A word beginning with a letter is a command e A word beginning with a number is a numerical value e Words are delimited by spaces tabs newlines brackets or an e Names of variables and commands are case insensitive in Simple Logo e All values are integers e Simple Logo unlike Logo will expect only one command per line That is a single command plus its argumen
4. strict_ilist gt lt instr gt lt strict_ilist gt loops lt repeat gt REPEAT lt expr gt lt strict_ilist gt conditionals lt if gt i IF lt cond gt lt strict_ilist gt function declarations lt fdecl gt TO identifier lt strict_ilist gt conditions for tests in IF statements lt cond gt lt condop gt lt expr1 gt lt expr2 gt lt condop gt LESS GREATER EQUAL NOTEQUAL Slogo 10
5. the turtle and could imagine how the turtle moved by playing turtle moving their bodies as the turtle would The turtle also makes learning basic programming concepts easier and more engag ing because it provides immediate feedback As a dialect of LISP Logo is a complex and powerful language For this project you will design and implement a much simplified version of Logo Simple Logo should retain the features most commonly used by beginning users so that it can be used to provide an introduction to com puter programming Terrific What do I need to start First of all you need a partner Then you need to decide who is going to work on which component of this assignment Only one member of the group will get credit for doing the GUI part The person that did not get credit for GUI will need to do the graphics component of the next assignment That way everyone will have an opportunity to hack some GUI code before the final project You need to decide who you will be working with by Saturday February 28th and sign up on the sheet outside the TA room Once you do this we will create a unix group that both mem bers of your group are in so that you can restrict access to your files The Making Logo Quick Package Simple Logo will consist of a basic turtle graphics package and support for a set of com mands allowing the user to control the turtle and the pen using basic programming constructs such as loops and sub
6. which assign a variable to have the value of another variable a number or a command For example x SUM 40 50 would be valid input The job of the parser is to match the appropriate command handler with the specified com mand name In matching a command name with a handler remember that you have to search not only the built in commands but also the user defined subroutines The parser can then pass control to the handler also giving the handler the list of arguments One way to think about the command interpreter is as a set of command handlers which each know how to execute a specific command Most of the handlers will be very straightforward the numeric operation handlers will need to make calculations and the turtle graphic commands will need to make calls to the turtle graphics library The loops conditionals and subroutine defi nitions will be slightly trickier Remember that the repeat if and to commands are the only commands which will have input on more than one line Subroutines are user defined commands with their functionality composed of existing logo commands You will also have to think about how to handle lists of instructions that correspond to each command Note that you do not have to handle passing parameters to your subroutines although your design should allow this simple extension Variables will also need to be dealt with You don t need to implement any concept of scope so you could just have a table of all of th
7. Due Dates Assignment Out Partner s Chosen Individual Designs Due Group Design amp Interfaces Due Logo Due Simple Logo Slogo CS32 Assignment 3 February 26 1998 Feburary 28 1998 11 59pm March 2 1998 11 59pm March 5 1998 11 59pm March 12 1998 9 00pm The following is a paid advertisement for Slogo by the CS32 TA staff Say hi to our hosts Don Cash and Money Lapre One special day in my third grade class they put three Apple Ile s in the back of Mrs Bailey s classroom and they were all running Logo Logo like BASIC was intended as an edu cational language and like BASIC is probably responsible for ruining several million potential programmers with its open encouragement of global variables and absurdly long spaghetti coded subroutines You re older now and have put aside childish programming techniques the Good Word of Design has filled you from head to toe But part of you misses the child like joy of cod ing in all capital letters and referring to a triangle as a turtle CS 15 made you feel guilty about this side of your personality but it never completely died Kite SN WSN MAR NEONA OIS RODAN ONS Mea NA A WORST wA SSS In this assignment your two conflicting halves will be brought into glorious union using the software engineering skills you have carefully cultivated since coming to Brown you will cre ate
8. drawing area and sends the turtle to the home CS position Like CLEAN and HOME PENDOWN sets the pen s position to DOWN PD PENUP sets the pen s position to UP PU PENDOWNP outputs 1 TRUE if the pen is down 0 FALSE if it s up PENDOWN Table 3 File Commands Command Description SAVE filename Saves the definitions of all procedures and variables in the named file LOAD filename Loads the definitions from the named file BYE Exits LOGO Slogo Table 4 Control Structures and Procedures Command Description REPEAT numOrVar runs instructionlist numOrVar times instructionlist IF varOrCommand instructionlist TO subr_name if varOrCommand is not O run instructionlist defines a new subroutine command named subr_name instructionlist When invoked the subroutine will execute the body of instructions included in the definition Table 5 Boolean Operations Command Description LESS num1 num2 outputs 1 TRUE if its first input is strictly less than its second or 0 otherwise FALSE GREATER num1 num2 outputs 1 if its first input is strictly greater than its second or 0 otherwise EQUAL thing thing2 outputs 1 if the two inputs are equal 0 otherwise NOTEQUAL thing1 outputs if the two inputs are not equal 0 otherwise thing2 If all of these tables seem confusing and you d just rather see the grammar for slogo here s all you need If this doe
9. e variables that exist and their current values Scope would be cool though and we re sure you could handle it but it s not required When a variable is passed to a command its value will need to be looked up Error checking As specified above we will expect some amount of error checking It should be fairly easy to check for parsing errors by checking each issued command against the set of legal commands and user defined procedures which comprise the Simple Logo name space Another measure of error checking to take is to count the number of argument tokens for each command and to com pare the expected number of arguments with the given number of arguments You should also think about how to identify and handle bad user input values I m so excited Where can I find out more To get a feel for how logo works we would suggest that you play around with the actual program which is in cs bin logo To leave logo enter the command bye in the logo turtle shell There are some sample logo files in course cs032 asgn logo examples Simple Logo should be able to read in and execute the procedures contained in the example files Note that SimpleLogo isn t compatible with Logo so don t expect the files for one to run in the other Note that these programs do not test the entire functionality your program should support Information about the Logo language and Logo commands can be found in detail in the user manual in cs lib lo
10. go usermanual Slogo 4 Wow In just one week I ve created Logo using the Making Logo Quick Package I have another week and I want more There is a lot of room for creativity and extras in this project but as always do not start implementing any of these until Simple Logo as specified is functional You are welcome to design your program to support any of these features Some ideas eVariable scoping and passing parameters to subroutines i e turning subroutines into procedures eAn enlarged command set see the Logo usermanual for ideas eMultimedia audio animation more complicated GUI More complex control structures eList processing functions and lists stacks queues and random access arrays eA snazzier turtle graphics package Cashing In We recommend you individually come up with a top level design before getting together with your group to work out the complete design You must meet with a TA on or before Thurs day March 5 to go over your design Please try to go meet a TA together rather than seperately You must give the TA a copy of your detailed fully annotated design i e commented object dia gram which the TA will keep and which will count as part of the grade for this assignment You should also bring a copy of the design for you to make notes on When you are finished with your program hand it in electronically by the end of the day Thursday March 12 1998 When you hand in your finished program
11. negative of its input PRODUCT num1 num2 outputs the product of its inputs QUOTIENT num1 num2 outputs the quotient of its inputs REMAINDER num num2 outputs the remainder on dividing num1 by num2 The result is an integer with the same sign as num2 Table 2 Drawing Operations and Turtle Commands Command Description FORWARD dist moves the turtle forward by the amount specified FD dist BACK dist moves the turtle backwards by the amount specified BK dist LEFT degrees turns the turtle counterclockwise by the specified angle LT degrees RIGHT degrees turns the turtle clockwise by the specified angle RT degrees SETXY xcor ycor moves the turtle to an absolute screen position Slogo 7 Table 2 Drawing Operations and Turtle Commands Command Description SETX xcor moves the turtle horizontally to a new absolute horizontal coordinate SETY ycor moves the turtle vertically to a new absolute vertical coor dinate HOME moves the turtle to the center of the screen 0 0 XCOR outputs the turtle s X coordinate YCOR outputs the turtle s Y coordinate HEADING outputs the turtle s heading in degrees TOWARDS xcor ycor outputs a heading the turtle should be facing to point from its current position to the given position SHOWTURTLE makes the turtle visible ST HIDETURTLE makes the turtle invisible HT CLEAN clears the drawing area the turtles statistics do not reset CLEARSCREEN erases the
12. ou will need to support Don This sounds great Where do I start The Simple Logo project can be broken down into two parts all of which you are respon sible for writing e Command parsing interpretation and maintenance of the global environment e Turtle Graphics Library TGL consisting of a display window and methods to move the turtle and draw with the pen Parsing involves processing commands token by token and checking for syntactical errors Interpretation means executing the code as it is understood by the parser The execution is likely to require graphical manipulation which is where the TGL comes in It should utilize X graphics calls and should be simple and well defined Remember that having a good design is key You should work with your partner to come up with a solid program design Hammer out interface specifications and know how the different parts interact and what functionality they will need from one another Before you start writing code it might be a good idea to write header files with empty code blocks and compile them together To move the turtle and draw with the pen you will need to have the parser interpreter graphics library interaction in place so you will need to know exactly how all three parts fit together As has been said a bazillion times there is no single perfect design Feel free to be cre ative Express yourself However keep in mind that functionality is essential and simplicity is beauty
13. routines When the Simple Logo user launches the interpreter from the com mand line it should bring up a turtle shell and a turtle graphics window The interpreter will need to receive parse and execute commands from the user reporting any errors it encounters along the way Simple Logo should provide functionality in the following areas e Basic turtle graphics Slogo users should be able to control the turtle by moving it forwards backwards changing its heading and showing hiding the turtle Drawing capabilities should be provided by pen manipulation The user should also be able to make turtle motion and pen queries Slogo 2 e Some basic logo instructions as described in Appendix A e Workspace management Users should be able to define and use subroutines Users should also be able to define and use global variables e Control structures loops and conditionals e Error handling Simple Logo should gracefully handle any errors that may occur while parsing and interpreting user given commands This includes providing appropriate error messages we ll leave it up to you to define appropriate e File I O The user should be able to load logo files into the interpreter and should be able to save the current working environment composed of user defined subroutines variables as well as turtle and pen information to a file Refer to the table of commands at the end of this handout for a full list of the built in com mands which y
14. sn t make sense to you review your notes from 31 or 51 If you re still stuck come see a TA It s worth knowing grammar for simple logo a program is a list of instructions lt prog gt n lt ilist gt an ilist is a list of instructions and function declarations lt ilist gt lt instr gt lt ilist gt lt fdecl gt lt ilist gt an instruction might be an assignment function call a conditional or a loop lt instr gt n lt asgn gt lt feall gt lt if gt lt repeat gt Slogo 9 an assignment always looks the same a variable gets an expression lt asgn gt lt var gt lt expr gt variables always look the same colon followed by an identifier lt var gt identifier expressions can look like anything they bottom out with vars and numerical constants lt expr gt number lt var gt SUM lt expr gt lt expr gt DIFFERENCE lt expr gt lt expr gt MINUS lt expr gt PRODUCT lt expr gt lt expr gt i QUOTIENT lt expr gt lt expr gt REMAINDER lt expr gt lt expr gt fcalls are either subroutine calls or built ins we don t bother putting in all the built ins here for brevity lt feall gt identifier are Imagine all the built ins from table 2 and 3 here blocks of code delimited by cannot contain function declarations unlike the top level instruction list so we introduce strict_ilist to be a list only of instructions lt
15. ts is to be terminated with the newline character Thus fd 50 rt 90 is syntactically valid while EG 50 PE 90 is not There is variable assignment A variable assignment can have one of three forms var_name COMMAND var_name other_var_name var_name number For example the following are valid foo SUM 12 34 bar foo fish 23 e Commands will be in prefix form that is the command name will precede the arguments e All commands return a value If no return value is defined the command should return 0 The variable TRUE should be defined to be 1 and FALSE should be 0 e The supported conditional is IF If the command or variable has a value of 0 the body of the IF should be skipped otherwise it should be executed IF lt command or variable gt instruction instruction e The supported loop is REPEAT The instructions in the body should be executed the number of times given by the value or variable REPEAT lt variable or number gt instruction instruction e The command name TO denotes the beginning of a subroutine definition The next argument should be the name of the subroutine Then the body of the subroutine is specified TO mysub instruction instruction Table 1 Math Operations Name Description SUM num num2 outputs the sum of its inputs DIFFERENCE num num2 outputs the difference of its inputs MINUS num outputs the
Download Pdf Manuals
Related Search