The PLT Scheme Environment

(Also see the documentation at http://docs.plt-scheme.org/ for more information.)

1. Starting the system

   PLT Scheme is available both as a text-based interpreter (MzScheme,
   invoked using "mzscheme") and as a GUI-based development environment
   (DrScheme, invoked using "drscheme"). 


   When you invoke MzScheme, a command processor starts running. It 
   gives you a prompt at the terminal. You can then type an 
   S-expression or load a program from a file. MzScheme evaluates 
   the expression or the program, prints its value, and then presents
   another prompt. To exit MzScheme, type "(exit)".


   The first time you run DrScheme, you need to select the language
   (that is, the dialect of Scheme) you wish to use. From the Language
   menu, select "Choose Language...", and then select "Module".

   When you run DrScheme, a split window appears. The top half is used 
   for defining procedures, and the bottom half is used for interaction
   (e.g. for testing your procedures, or for evaluating simple 
   expressions). Note that procedures you define in the top window must 
   be loaded using the "Run" button before they can be tested in the 
   bottom window.


2.  Files

    Source files must start with the line:

       #lang scheme

    To load a source file in MzScheme, use

    (enter! "filename")

    where filename is the name of your file (e.g. a1a.ss or a1a.scm).

    
    To load a source file in DrScheme, simply use File->Open. Note that
    once the file is loaded, you need to Run it in order for the 
    interaction half of the window to appear.


3.  Debugging

    To use DrScheme's debugging tools, click on Debug (instead of Run).
    DrScheme allows you to set breakpoints, step through code, view the
    call stack, and examine variables. You can set breakpoints by right-
    clicking on the opening brackets of S-expressions. Beyond that, the
    debugging tools are mostly self-explanatory.