Frequently Asked Questions

Unlike most programming languages, there is no "how-to" book that I can recommend to learn scheme. If you're a beginner, I suggest reading The Structure and Interpretation of Computer Programs. You can also read The MIT/GNU Scheme documentation.

In scheme, the ; character is the comment character. But historically, the number of ; characters used has meaning. Four semicolons describe the file. Three describe the next function. Two describe the next chunk of code. One describes the line. As in:

;;;; Mathematical Functions
;;; Fibonacci numbers
(define (fib n)
  ;; Calculate the nth Fibonacci number recursively
  (if (< n 2)
      1                                 ; base case
      (+ (fib (- n 1)) (fib (- n 2)))))

There is also the #| ... |# multi line comment, similar to the /* ... */ comment in C and C++. This comment is useful for including test cases. If you were completing the definition of fib for a pset, you might use a multi-line comment to include test cases like so:

#|
 (fib 5)
;Value: 8

 (fib 20)
;Value: 10946
|#

Note that you can evaluate the (fib 5) and (fib 20) scheme forms using C-M-x or M-z even though they are in comments.

Emacs knows about scheme's commenting conventions. You can insert and remove comments using M-;. If you select a region of code, it will comment or uncomment out the entire region.

The easiest way to grok it is by reading other people's well-formatted code. As a start, the format of parentheses are not like in C; end parentheses should go together.

For more guidelines, go here:

http://community.schemewiki.org/?scheme-style

Practice, practice, practice! I highly recommend printing the emacs reference card and keeping it close to your computer at all times.

Emacs automatically correctly indents your code for you, but if your code is somehow not indented properly, here are some ways to indent it.

In Edwin and Emacs, pressing tab indents the line. Pressing C-M-q indents the sexp to the right of the point.

In Emacs, pressing C-x h selects the entire buffer. Pressing tab will then indent the entire file.

Please email me and GJS your code. As long as you include the code, test cases, and results, you'll be fine.

I've started taking my own notes in org mode. Here is a reference card to get you started.

You can also read more about org mode at their home page. You may also be interested that this webpage (and the Don't Panic! memo) was built in org-mode.