On Wed, 2007-05-02 at 02:01 -0700, Erick Tryzelaar wrote:
> I just came across this in flx_stdlib.pak:
>
> ...
> @h=tangler('lib/flx_platform.flxh','data')
> @select(h)
> #define true case 1 of 2
> #define false case 0 of 2
>
> @plats = ["WIN32","POSIX","LINUX","MACOSX","CYGWIN","SOLARIS","BSD"]
> @for i in plats:
> if(eval(i)==1):
> tangle("#define " + i + " true")
> else:
> tangle("#define " + i + " false")
> @#
>
> macro val true = case 1 of 2;
> macro val false = case 0 of 2;
> ...
>
> Is there any reason why "true" and "false" are seemingly defined twice?
They're not. The first case is a #define and the second a macro val.
There is no overlap between these: #define's ONLY work
in #preprocessor directives, macros only work in the parse tree
after preprocessing and parsing is finished.
The preprocessor and macro processor share a common set
of evaluation routines for folding constants
(see src/flx_constfld.ml) and use the same language for
them as Felix as a whole.
However the scopes/environments/text that they're applied
to are strictly disjoint:
#define fred 1
print fred; // undefined symbol fred!
macro val joe = 1;
#if joe == 1 // un #defined symbol joe
--
John Skaller <skaller at users dot sf dot net>
Felix, successor to C++: http://felix.sf.net
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