Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!uw-june!david
From: david@cs.washington.edu (David Callahan)
Newsgroups: comp.lang.c++
Subject: Re: #pragma once (was Re: A solution to the multiple inclusion
Message-ID: <9635@june.cs.washington.edu>
Date: 30 Oct 89 14:59:08 GMT
References: <14240@well.UUCP> <2082@plx.UUCP> <1989Oct27.163755.12976@paris.ics.uci.edu> <23464@cup.portal.com>
Reply-To: david@june.cs.washington.edu.cs.washington.edu (David Callahan)
Organization: Tera Computer Co., Seattle WA
Lines: 35

In article <23464@cup.portal.com> John_-_Nagle@cup.portal.com writes:
>
>     Common LISP has "require", which has the right semantics for this
>situation.  Perhaps we could use that keyword.
>
...
>     So how about
>
>	#require FILENAME
>
>as the one-time inclusion mechanism for C++. 
>
>     The ultimate goal is that all include files contain "require" statements
>for everything they need, so that order of inclusion in the ".c" files isn't
>an issue and the user of a library doesn't have to worry about including
>too little or too much.

I think you'd want some insulation from the vagaries of file systems.
How about:

	#pragma require function "file"

where "file" defaults to function if it is not provided.
And in "file":

	#pragma provide function

Another advantage of this mechanism is that header files could be
collected into a library and some tool similar to "ranlib" used to
cross-refedrence function to filename. Then of course, its one small
step to treating every "class foo { ... }" as implying "provide foo".

-- 
David Callahan  (david@tera.com, david@june.cs.washington.edu,david@rice.edu)
Tera Computer Co. 	400 North 34th Street  		Seattle WA, 98103