Newsgroups: comp.lang.c
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Variable Parameters
Message-ID: <1989Dec31.013746.2349@utzoo.uucp>
Organization: U of Toronto Zoology
References: <1169@zip.eecs.umich.edu>
Date: Sun, 31 Dec 89 01:37:46 GMT

In article <1169@zip.eecs.umich.edu> bagchi@dip.eecs.umich.edu (Ranjan Bagchi) writes:
>        I'm working, currently, on a project that involves a function that
>could take any number or arguments.  I would like to pass it only
>those arguments, i.e. no "flags" at the end which tell the function
>to stop.

Your function has to have some way of knowing how many arguments there
are, or which is the last argument.  The language does not provide any
built-in way for you to discover this.  The usual approaches are a
terminator argument of some kind, an argument count passed as the
first argument, or an implicit count embodied in an early argument
(e.g., you can tell how many arguments a printf() has by analyzing
the format string).  You have to do one of these things.

>        I'm using ANSI C, and believe my options are either to pass
>the function an array, or to use the elipsis for unspecified.

By far the simplest method is to pass an array with either a terminator
flag in the array or a count as a separate argument.  The ellipsis will
not solve the problem for you, and proper use of it is complex.
-- 
1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
1989: birds nesting in engines | uunet!attcan!utzoo!henry henry@zoo.toronto.edu