conditional code segments

[Matt Wette <matt.wette@gmail.com>]

In C I can use `#ifdef' .. `#endif' to "comment out" code segments.

In Scheme, one can use `#|' and '|#' which is OK but requires dealing with both ends of the
segment to switch on / off.  And emacs (v 24.5) scheme mode does not always fontify the buffer
correctly with #|...|#.

I can use (if #f (begin ....)) but it's not pretty and indents 4 spaces (or an ugly 1 space).

I tried using cond-expand but it does not work as expected:
   scheme@(guile-user)> (cond-expand-provide (current-module) '(abc))
   $1 = (abc)
   scheme@(guile-user)> (cond-expand (abc #t))
   While compiling expression:
   Syntax error:
   unknown file:2:0: cond-expand: unfulfilled cond-expand in form (cond-expand (abc #t))

My current attempt is to add this:

   (define-syntax-rule (if-true form ...) (begin form ...))
   (define-syntax-rule (if-false form ...) (begin))

   (if-false
    (define x ...)
    ...
    )

   (if-true
    (define x ...)
    ...
    )

Any other solutions / suggestions?