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From: jmartin@secola.Columbia.NCR.COM (John Martinez)
Newsgroups: comp.lang.c
Subject: You _CAN_ "stringize" tokens in (some) K&R pre-processors
Message-ID: <323@secola.Columbia.NCR.COM>
Date: 2 Apr 91 00:21:14 GMT
Reply-To: jmartin@secola.Columbia.NCR.COM (John V. Martinez)
Distribution: comp.lang.c
Organization: NCR NPD Columbia
Lines: 64


	I seem to recall a thread of discussion a couple of weeks ago
about how to "stringize" a token using the K&R C preprocessor (ANSI C
provides the # operator to do this.) Anyway, as I recall, the concensus
was that it couldn't be done. (At least, no one submitted a method, as 
far as I know...)

	Well, now I had to try (the Mt. Everest principle, you know,)
so I locked myself in my laboratory with a six-pack of Mountain Dew and
a cold pizza, until I discovered a magic spell that (sort of) did the
trick:

#define quote "
#define stringize(A)  quote A"

this is _almost_ right; stringize(foobar) --(magic)--> " foobar"

	The next problem is to remove the leading space (if you don't
put a space between 'quote' and 'A' in the macro, it sees 'quoteA' as a
token, which doesn't resolve to anything interesting..)

Another slice of cold pizza later.....
-(POOF)-
*********
static char *global_char_ptr;  /* 'static' is just a personal preference. */
#define quote "
#define stringize(a) (global_char_ptr=quote a",++global_char_ptr)

main()
{
int foo=5;

printf("%s = %d\n",stringize(foo),foo);
}
*********
_my_ system's preprocessor converts the printf line to:

printf("%s = %d\n",(global_char_ptr=" foo",++global_char_ptr),foo);

which outputs:
foo = 5

Voila!

NOTE: I'm sure there are lots of netters who:
a) already knew about this
b) saw a solution just like it in a posting I never saw 
	_or_
c) think the whole discussion is dumb since "the whole world should have
bought an ANSI C compiler 4.7 microseconds after the standards were
signed, no matter what the cost, and if you can't find a compiler you
can just write your own in 2 hours, otherwise you're not a real programmer"

	I have a established a special account, devnull@TheAbyss for
you to reply by mail. Seriously - I posted this because I thought it
would be of use to someone, and I am pretty darn happy about it, so
don't rain on my parade, ok?


---
John V.Martinez                   "Yeah, I got a college degree, but somehow I
NCR Network Products Division      managed to learn something in spite of it."
jmartin@secola.Columbia.NCR.COM
(803)772-8854 vplus:633-8854