We'll use DrRacket, version 5.3. It is installed on the windows machines in the undergrad labs and on attu, or you can download it for a personal machine.
On the Windows machines in the lab, DrRacket is here:
All Programs / DEV TOOLS & LANGUAGES / Racket / DrRacket
You can also double-click on a saved Racket source file.
On Linux, start it by typing drracket to the shell prompt. You'll need to use XWindows -- DrRacket will come up in a separate window.
Finally, you can download it and install it on a personal machine from http://racket-lang.org/download. It's free.
The first time you use DrRacket, click on “Choose Language” in the lower left and then select “Use the language declared in the source.” The text #lang racket should appear in the upper definitions pane. Click “Run”.
DrRacket should remember this choice henceforth.
#lang racketThis tells DrRacket that your file is in the Racket language and not some other language. You can have lines of comments before this line.
(provide (all-defined-out))This line is, at least for the time being, working around Racket's module system. In Racket, each file is its own module and this line is making all top-level definitions externally visible, which is not the default. You do not need this line to use your definitions in the REPL (the bottom buffer). You do need this line (or another approach) to use your definitions from a second testing file.
(require "octopus.rkt")where octopus.rkt is the file with the code you want to test. Put both files in the same directory/folder on your computer. Your testing file does not need (provide (all-defined-out)).
Use the "Debug" button to debug programs, and also to understand how recursive functions are operating. Another useful command is "Check Syntax", which of course checks the syntax, but also lets you see the bindings of variables. (Try hovering the mouse over a variable -- good to help understand lexical scoping.)