Path: utzoo!utgpu!watserv1!watmath!att!cbnewsh!ijk
From: ijk@cbnewsh.ATT.COM (ihor.j.kinal)
Newsgroups: comp.lang.c
Subject: Arrays of functions - calling them with different number of args.
Message-ID: <8553@cbnewsh.ATT.COM>
Date: 1 Mar 90 14:08:34 GMT
Distribution: na
Organization: AT&T Bell Laboratories
Lines: 36

I've set up an array of 50 functions, to be called with one standard
argument, and my function call looks like this [which particular
function to be called is determined by the action_ind.

			action_tbl [ action_ind ] ( one_arg )
				
	where the one_arg is a pointer to a particular type.
	
Now, I want to add some functions that will have two arguments.

The question is, how do I express the call to that function
both simply and portably?

Obviously, I could provide a list of arguments for each function
in my table, and I could test if an arg two is present, then I call

			action_tbl [ action_ind ] ( one_arg, two_arg )

and otherwise, call the old way.  This seems incredibly clumsy.

Alternately, I could call EVERY function with two arguments,
with the second being null for the actual one-arg functions.

Note that I don't want to go back to the source and add a dummy argument
to all the old functions.

Given that my machine passes the first 4 arguments as registers,
I believe that this should work - however, it strikes me as potentially
non-portable on some stack machines.

What I really want is to construct an arg list and pass that to my
function call, but I can't figure how to do that.

Any help will be appreciated,
Ihor Kinal
att!cbnewsh!ijk