Testing if a function is defined in a module

[Carlos Smith]

"Kirk McDonald" <kirklin.mcdonald at gmail.com> wrote in 
message news:erggra$lc1
: static if (is(typeof(&YYUSERINIT))) {
:     // Do stuff with the function
: }
: However, I can't help but wonder what situation you're in 
where you need
: to check this directly. I'm just guessing, here, but you'd 
probably be
: better off using a version flag:

I am trying to add D support to flex. Without completly
rewriting it.

GNU programs use the preprocessor a lot, and in ways
not easy to translate to D.

Given a grammar, flex generate a C lexer for that grammar.
The user can define a macro YYUSERINIT. That macro will be
expanded if the test:

#ifdef YYUSERINIT
    YYUSERINIT();
#endif

is satisfied. flex does not know, and does need to know
if YYUSERINIT is defined.

But, he [the user] may also not define it, and everything 
will compile
ok.

Your first suggestion is exactly what i am looking for.

That can be also used to generate a default version for
a function, in the case the user does not define his own.

eg:
int yywrap( ) { return 1;}


Thanks a lot.