Re: [Swig-user] Blimey! Swig macro insanity

[David B. <dav...@da...>]

SWIG never runs the preprocessor inside %{ ... %} blocks.   That's  
why you're not seeing anything there :-).

-Dave

On Jan 22, 2008, at 4:55 PM, David Piepgrass wrote:

>> From: David Beazley <dav...@da...>
>>
>> So, don't ask me why, but I was sitting here thinking about the Swig
>> macro preprocessor this morning and started wondering if I could
>> actually write recursive functions in the preprocessor.   Well, the
>> answer seems to be yes.   Check out some examples:
>>
>>      %define FACTORIAL(N)
>>      #if N == 0
>>      1
>>      #else
>>      (N)*FACTORIAL(N-1)
>>      #endif
>>      %enddef
>
> SWEET! I'll be delighted if I can think of a use for this! Eat that,
> ordinary C preprocessor :P
>
> Only, for some reason it doesn't work in C code:
>
> %define FACTORIAL(N)
> #if N == 0
> 1
> #else
> (N)*FACTORIAL(N-1)
> #endif
> %enddef
> %constant FOO = FACTORIAL(6); // OK
>
> %{
> 	FOO;                    // nothin'
> 	FACTORIAL(6);
> %}
>
> See that last part? The output is not preprocessed.
>
> And guess what kind of failure you get from....
>
> %define RECURSIVE(N)
> RECURSIVE(N+1)
> %enddef
> %constant UH_OH = RECURSIVE(0);
>
>
>
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