Using Dr. Racket
The following are helpful hints for using Dr. Racket for coursework and for homework assignments. These pointers apply to many other Scheme interpreters and IDEs, too.
-
When you want the interpreter to evaluate an expression, enter it
in the Interactions window and hit
return
. You can get to the Interactions window by choosing it from the File menu or by executing the code in the Definitions window. - Dr. Racket lets you know the state of your expression by highlighting the expression surrounded by the parenthesis at your cursor. Just place your cursor to the left of a left parenthesis or to the right of a right parenthesis. This will help you manage "all those parentheses".
-
Typing
return
while in the middle of an expression will drop the cursor to the next line, indented in a suitable fashion, and allow you to type more text. But it will not cause Dr. Racket to evaluate the current expression. -
You can add a comment to your Racket code by using
;
, the semi-colon. All text following a semi-colon is ignored by the interpreter when a file is loaded. -
Comments are intended primarily for code in files. If you type
a comment during an interactive session, the interpreter will
require you to follow up with a valid expression, even if you
had typed one on the line before your comment. For example:
> 12 ;; comment 13 ;; comment 14 12 13 14
-
At any time, you can save the contents of the your Dr. Racket
Interaction window as a plain text file, using options
available on the standard
File
menu. You may find this handy when you would like to take a trace of an interaction when you leave the lab, say, for debugging or for showing your instructor what you've been doing.