Path: utzoo!mnetor!uunet!husc6!cmcl2!brl-adm!brl-smoke!gwyn
From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: procedure pointer question
Message-ID: <7108@brl-smoke.ARPA>
Date: 15 Jan 88 21:11:01 GMT
References: <861@xn.LL.MIT.EDU>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 25

In article <861@xn.LL.MIT.EDU> cogen@XN.LL.MIT.EDU (David Cogen) writes:
>Both invocations of fun work and give the correct result.

In almost all contexts, the function designator (i.e. name) is
converted into a pointer to the function.  When you call a function,
the thing before the "(arguments)" part it is required to be a
pointer to a function of appropriate type.  This is what some
current C compilers actually do and is what X3J11 decided on for
the ANSI C standard.  However, it's not how K&R described it.

Note that the following invocations will all be valid and all do
the same thing:

	extern double sin( double );
	double x;

	x = sin( 2.0 );
	x = (&sin)( 2.0 );
	x = (*sin)( 2.0 );
	x = (**sin)( 2.0 );
	x = (***sin)( 2.0 );
	/* etc. */

You can do similar things with objects that are explicit pointers-
to-functions.