Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!purdue!haven!adm!cmcl2!lanl!jlg
From: jlg@lanl.gov (Jim Giles)
Newsgroups: comp.lang.c
Subject: Re: ambiguous ?
Message-ID: <14091@lanl.gov>
Date: 18 Oct 89 22:03:13 GMT
References: <1989Oct17.203733.23121@utzoo.uucp>
Organization: Los Alamos National Laboratory
Lines: 18

From article <1989Oct17.203733.23121@utzoo.uucp>, by henry@utzoo.uucp (Henry Spencer):
> I could have sworn that a good many things were officially undefined in
> Fortran (66 or 77, take your pick), such as the values of local variables
> after return from a function.  I could be wrong -- I'm not a Fortran guru.

That's a different definition of _undefined_ and you know it.  The Fortran
use is a description of the status of those variables.  In C, the _behaviour_
of the program is what's undefined.  The closest thing in Fortran is the
explicit optimization allowed in expressions (ie. the expression can be
reordered in by _mathematically_ valid identities).  However, Fortran
provides an _efficient_ way to override such optimization.  C has _many_
more contexts which are _both_ undefined and without efficient ways
of overriding the ambiguity.

This is not to say that Fortran is perfect - it isn't.  But it is a better
defined and more clearly specified language.  I know several people who
don't use C simply because its behaviour is deliberately undefined and
there is no clear way of explicitly overriding such ambiguities.