Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!tut.cis.ohio-state.edu!rutgers!cmcl2!lanl!jlg
From: jlg@lanl.gov (Jim Giles)
Newsgroups: comp.lang.c
Subject: Re: ambiguous ?
Message-ID: <14125@lanl.gov>
Date: 25 Oct 89 22:31:08 GMT
References: <6675@ficc.uu.net>
Organization: Los Alamos National Laboratory
Lines: 31

From article <6675@ficc.uu.net>, by peter@ficc.uu.net (Peter da Silva):
> In article <14114@lanl.gov> jlg@lanl.gov (Jim Giles) writes:
>> [... comments about the continuing lack of an approved C standard ...]
> Compare it to X3J3.

I dare not!  I've been accused (incorrectly) of hold C up to scrutiny
only vs. Fortran.  This, is another case in which someone else just
assumes that I will be defensive about Fortran.

But, what the hell - since you mention it.  X3J3 _has_ successfully
passed 2 previous standards.  The present revision has only gone to
two public reviews so far.  X3J11 has gone to 3 public reviews and
now faces a class action suit - they still haven't passed even one
standard!

> [... Examples like X = 0 * FUNC(Y) ...]
> You say that X3J11 is the only standard which allowed ambiguous constructs.
> Looks like that statement is inoperative.

Not at all.  The Fortran standard refers to the above behaviour as
"implementation defined".  This means that the implementation _should_
define the meaning of the expression.  Most implementations choose to
let the optimizer have free rein (and therefore, the _implementation_
is responsible for the ambiguity).  In my opinion, this doesn't meet
the requirements of standard conformance since the implementation
_should_ define the semantic meaning of the construct.

However, X3J11 will be the only ANSI language standard which _specifically_
_doesn't_ require an implementation to provide a definition of some
behaviours in order to be considered comforming.  Therefore, the ambiguity
is specifically allowed by the proposed standard.