Using Dr. Racket
The following are helpful hints for using Dr. Racket for
coursework and for homework assignments. These pointers apply to
most Scheme interpreters and IDEs.
- 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
- 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.
Eugene Wallingford .....