Title: Building an Interpreter.

Instructions:  Work with a partner in the class to implement an interpreter for a subset of the LOGO language. LOGO is a programming language intended for use in introducing K-12 students to computer programming. It was developed in the early 1970s at Bolt, Beranek and Newman, Inc., in Cambridge, Massachusetts by Feurzig, Bobrow, and Papert. It has various features in common with Lisp, and so it's easier to build an interpreter for LOGO in Lisp than to do it, say, in a lower-level language like C that doesn't have list manipulation facilities built-in.
 
For your LOGO subset, you should handle most of the non-graphics parts of the language. Any support you provide for turtle graphics is optional, and to use graphics, you would have to get involved with a graphics package such as Allegro's Common Graphics or the Common Lisp X-Windows graphics facilities available under Linux.
 
Your LOGO subset should be capable of handling a recursive factorial function call, for example. As a guide to what your interpreter should handle, take a look at the reference manual for rLogo, a small Logo system written as a Java applet by Randall Embry. You don't have to implement any of the commands listed there under "Drawing" or "Visual Effects". Under "Programming", the command you should implement are show, params, to, and make.
 
If the user enters invalid LOGO code, your program should report an error but not break out of its LOGO read-eval-print loop.
 
Policy on using web resources: You are welcome to consult any available resources you find on the web. However, the code you write for this assignment should be YOUR OWN. If you end up using ideas of others that you find on the web, you should: (1) give credit in your own program by citing, in a comment and in the documentation, the author and the web address for the idea or code sample, (2) explain how you are using that idea or code sample, as in ``this function is modelled after the PARSECOMMAND implementation in "...
 

The online submission form for this assignment is on abstract.cs.washington.edu.
Each team should submit two files: logo.lsp and readme.txt.
logo.lsp is to be a self-contained LISP program containing the code for the LOGO interpreter. To run the interpreter, after logo.lsp has been loaded, the user must type "(logo)" at the LISP prompt. The first thing the interpreter must do, before accepting any user input, is to print out the students' names. (Points will be deducted for not following this specification precisely.)
readme.txt is to be a PLAIN TEXT file specifying any assumptions in LOGO program formatting that were made. (Points will be deducted for any unspecified formatting assumptions.)