[gambit-list] Null pointer in scheme

Marc Feeley feeley at iro.umontreal.ca
Sat May 12 11:13:43 EDT 2007


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On 12-May-07, at 10:19 AM, David St-Hilaire wrote:

>     (set! dev (createDevice EDT_OPENGL (vector 800 600) 16 #f
>     use-shadows? #f 0))
>
> which when executed gives me the following problem:
>
>     [dave at localhost demo]$ ./demo
>     *** ERROR IN demo-main -- (Argument 7) Can't convert to C pointer
>     (createDevice 5 '#(800 600) 16 #f #f #f 0)
>
> Can anyone tell me would I should do...? I know that the same line in
> c++ works fine:
>
>     createDevice( video::EDT_OPENGL, dimension2d<s32>(640, 480), 16,
>                       false, false, false, 0);
>

#f is the Scheme value corresponding to the C NULL.  So you need to do:

(createDevice 5 '#(800 600) 16 #f #f #f #f)

or

(define NULL #f)
(createDevice 5 '#(800 600) 16 #f #f #f NULL)

Marc

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