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From: ahuttune@niksula.hut.fi (Ari Juhani Huttunen)
Newsgroups: comp.std.c++
Subject: Variable arguments (Was Re: type/member tags
Message-ID: <AHUTTUNE.91Mar2144431@silver-surfer.hut.fi>
Date: 2 Mar 91 13:44:31 GMT
References: <DSOUZA.91Feb24173454@optima.cad.mcc.com> <27C95D3A.1715@tct.uucp>
	<1991Feb27.154311.782@csc.ti.com> <27CD159D.6581@tct.uucp>
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Organization: Helsinki University of Technology, Finland
Lines: 31
In-Reply-To: chip@tct.uucp's message of 28 Feb 91 14:37:17 GMT

Suppose I want to write a function that takes as its arguments any number
of integers and returns the largest of these integers. This can be implemented
using constructs already found in the language. IF you a) tell the function
as the first argument how many integers you will supply to it or b) as the
last argument you give a predefined constant that means there are no more
arguments. This is error prone, I think.

The problem is that C++ doesn't give any means to check how many arguments
were supplied or their types.

If typeof() would be added to C++, the problem could perhaps be solved
this way:

int max(int x1 ...) {
	va_list argp;
	va_start(argp, x1);
	while(typeof(*argp) == int) {
		int x2 = va_arg(argp, int);
		if(x2>x1) x1=x2;
	}
	va_end(argp);
	return x1;
}

When there are no more arguments, typeof(*argp) == void.
--
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I I__I I__I I__I I__I I__I I__I I__I I__I I__I I__I I__I I__I I__I I__I I__I I_
Ari Huttunen      A computer is like a house of cards. Not as reliable,
                  but it has an equal number of incompatible parts.
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