Path: utzoo!attcan!uunet!ccicpg!felix!arcturus!evil
From: evil@arcturus.UUCP (Wade Guthrie)
Newsgroups: comp.lang.c
Subject: Re: Passing types to a subroutine
Summary: how about unions?
Message-ID: <2553@arcturus>
Date: 11 Nov 88 18:24:25 GMT
References: <14457@mimsy.UUCP> <14461@mimsy.UUCP>
Organization: Rockwell International, Anaheim, CA
Lines: 52

In article <14461@mimsy.UUCP>, chris@mimsy.UUCP (Chris Torek) writes:
> In article <14457@mimsy.UUCP> sjr@mimsy.UUCP (Stephen J. Roznowski) writes:
> >I'm in the process of developing a piece of code that needs
> >to be portable across several different machines.  What I
> >need to do is something of the following:
> [edited]
> >	subroutine(...., <float array>, ...);
> >	subroutine(...., <double array>, ...);
> >
> This is easy: you cannot do it at all in C.

how about using unions -- something like

union types
{
	float *f;
	double *d;
};

#define FLOAT	1
#define DOUBLE	2

subroutine(...,fred, type);
union *fred;
int type;
{
	. . .
	switch(type)
	{
		case(FLOAT):
			. . . fred->f . . .
			break; 
		case(DOUBLE):
			. . . fred->d . . .
			break; 
		default:
			/* error */
	}
	. . .
}

It's a little cumbersome, but it gets you there -- I used pointers
to floats and doubles because, in most cases, they act like arrays.
I've used things like this and it seems to work okay.


Wade Guthrie
Rockwell International
Anaheim, CA

(Rockwell doesn't necessarily believe / stand by what I'm saying; how could
they when *I* don't even know what I'm talking about???)