Re: conditional code segments

[Alex Vong <alexvong1995@gmail.com>]

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Matt Wette <matt.wette@gmail.com> writes:

> 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?

Maybe you can try to use #; to comment out s-exp? I prefer this way
because it feels very lispy to me.

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