Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uwm.edu!bionet!ames!sgi!shinobu!odin!delrey!shap
From: shap@delrey.sgi.com (Jonathan Shapiro)
Newsgroups: comp.lang.c++
Subject: Re: default argument discussion
Message-ID: <5102@odin.SGI.COM>
Date: 9 Mar 90 23:37:39 GMT
References: <1006@xyzzy.UUCP>
Sender: news@odin.SGI.COM
Organization: Silicon Graphics, Inc., Mountain View, CA
Lines: 35

>langley@bigbird.rtp.dg.com (Mark L Langley) suggests that the following
>should be legal:
>   
>      void bar(int x=i+j) {
>      printf("%d\n", x);
>      }
>   
>      main() {
>      int i=20, j=30;
>       bar();
>       }
>   ...I intend to propose this as a change in ANSI C++, and have already
>   proposed it to AT&T in private correspondance...
>
>Mark Langley
>langley@dg-rtp.dg.com

This is a great example of why language design should be left to
people who know what they're doing.

C already has a facility for doing this.  It is called a macro.

The problem with what you suggest is that the function definition site
needs to know lots and lots of things about ALL function use sites.
It also would be altogether impossible to implement this across files
today.

Functions should be isolated - they should not care who calls them,
except to the extent that they specify requirements in the form of
arguments.  The above proposal violates this any number of ways.

Try proposing it to the BASIC committee.  They love this sort of
stuff.

Jonathan Shapiro