Path: utzoo!attcan!uunet!husc6!uwvax!umn-d-ub!nic.MR.NET!tank!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: Passing types to a subroutine
Message-ID: <14485@mimsy.UUCP>
Date: 11 Nov 88 02:09:39 GMT
References: <14461@mimsy.UUCP> <32119@bbn.COM>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 44

In article <32119@bbn.COM> mesard@bbn.com (Wayne Mesard) writes:
>Or, how 'bout using a good old union to get rid of the extra param:

You can do this, but not as coded.  (Original code appears below.)
Instead, you must augment main() with a `union ptr' variable, and
change the calls to

	u.f = f;
	sub(0, u);
	u.p = d;
	sub(1, d);

The code below is not type-correct and WILL NOT WORK on (eg) a Pyramid.
I would also suggest using TYPE_FLOAT and TYPE_DOUBLE rather than the
literal 0 and 1 constants.

- union ptr {
-     float *f;
-     double *d;
- };
-
- enum whichtype {TYPE_FLOAT, TYPE_DOUBLE};
-
- main()
- {
-     void sub();
-     float f[10];
-     double d[10];
-
-     f[1] = 1.234;
-     d[1] = -5.432;
-     sub(0, f);
-     sub(1, d);
-     printf("Incidently, the sizeof the union is %d\n", sizeof(union ptr));
- }
-
-
- void sub(t, p)
- enum whichtype t;
- union ptr p;
[rest deleted]
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris