Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-tis!ames!amdcad!sun!quintus!ok
From: ok@quintus.uucp (Richard A. O'Keefe)
Newsgroups: comp.lang.fortran
Subject: Re: Fortran versus C for numerical analysis
Message-ID: <344@quintus.UUCP>
Date: 2 Sep 88 11:13:40 GMT
References: <893@amelia.nas.nasa.gov> <3064@lanl.gov> <338@quintus.UUCP> <3534@s.cc.purdue.edu>
Sender: news@quintus.UUCP
Reply-To: ok@quintus.UUCP (Richard A. O'Keefe)
Organization: Quintus Computer Systems, Inc.
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In article <3534@s.cc.purdue.edu> ags@s.cc.purdue.edu.UUCP (Dave Seaman) writes:
>In article <338@quintus.UUCP> ok@quintus.UUCP (Richard A. O'Keefe) writes:
>[I said it badly, so I shan't quote it]
>On the contrary, Fortran's parentheses control only grouping and have
>nothing to do with evaluation order.

Oops, sorry, expressed myself badly.  When writing "evaluator order"
I had in mind evaluate of _operators_, not of _operands_.

What I meant was that there is no method of saying "this grouping is
just syntactic so that I can read the expression, mathematical laws may
be applied".  The point is that some expressions can't be written
without using parens, and there is no way of distinguishing those parens
from ones that you *want* to have the special effect.  For example,
unless I am mistaken, (1.0+X)*2.0 must be evaluated that way rather than
as 2.0+2.0*X. Sometimes you care, but sometimes you don't. In this
particular example, unless you want to do part of the calculation
yourself, you have to put the parens in to get around the operator
priorities.  If, however, I write 2*I+2, the compiler *is* free to
rearrange this as 2*(I+1).  Isn't it?