[racket] (if ...) form without an else

Hi Lothar,

The if statement in Racket always requires three arguments:

(if<http://docs.racket-lang.org/reference/if.html?q=if&q=mapcar&q=map&q=foldl&q=take&q=append*&q=foldl&q=number-%3E&q=vector&q=for/&q=set#(form._((quote._~23~25kernel)._if))>
 test-expr then-expr else-expr)

if you only want a "then-expression", use "when" or "unless"
if you want more expressions, use "cond",  cond is a powerful and compact
construct in Racket

-Joe

On Wed, Apr 11, 2012 at 11:42 AM, lothar atheling <lothar_ at warpmail.net>wrote:

>
> usually an (if ...) form without an else part does not cause an error.
>
> but sometimes it does, as the following shows:
>
>
> if: bad syntax (must have an "else" expression) in: (if isinitialised
> (expose))
>
> why the different behavior?
>
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