[gambit-list] check vs null

Marc Feeley feeley at iro.umontreal.ca
Sat Feb 14 18:26:46 EST 2009


On 14-Feb-09, at 5:32 PM, lowly coder wrote:

> it works now; thanks!
>
> the main reason I posted to gambit rather than #scheme ... is that  
> this seems a C-FFI (thus implementation specific question, not a  
> generic scheme question)
>
> if I'm wrong ... please point out what scheme standard defines how  
> NULLS from C-FFI/land is handled in scheme?


If you define get-foo this way

(define get-foo (c-lambda () (pointer foo) "get_foo"))

then the C NULL maps to the Scheme #f.  On the other hand, if you want  
to exclude the possibility that the pointer is NULL then define it  
this way

(define get-foo (c-lambda () (nonnull-pointer foo) "get_foo"))

These are Gambit specific things.

Marc




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