On Wed, Mar 30, 2011 at 11:31, John Sampson <jrs....@ntlworld.com> wrote:
> Hello -
>
> I am going through TYSIFD which is said to be compatible with mzScheme.
>
> Descriptions of macros seem to be different depending which book one reads.
> TYSIFD advises the reader to 'require' the defmacro library
> - '(require (lib "defmacro.rkt"))' when using Racket (I assume) - and gives
> the example
>
> (define-macro when
> (lambda (test .branch)
> (list 'if test
> (cons 'begin branch))))
btw, try substituting the last two lines with:
(list 'if test
(cons 'begin branch)
#f)))
the problem is that if's in racket must have both arms, while in other
dialects they can be one-armed.
Cheers
P.
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