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From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.fortran
Subject: Re: Fortran versus C for numerical analysis
Message-ID: <13570@mimsy.UUCP>
Date: 15 Sep 88 05:26:00 GMT
References: <893@amelia.nas.nasa.gov> <3064@lanl.gov> <820@cernvax.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 28

In article <820@cernvax.UUCP> hjm@cernvax.UUCP (Hubert Matthews) writes:
>Consider the following cases:
>
>      I = (5 / 4) * 5		(I gets 5)
>
>      I = 5 / (4 * 5)		(I gets 0)
>
>      I = 5 / 4 * 5		(I gets 5 in F77, I gets something in C)

I gets 5 in C (even in K&R 1st ed. C).  The arithmetic operators group
left-to-right, and while

    The order of evaluation is not specified for associative and
    commutative operators like * and +

(K&R 1st ed., p. 37), the divide operator is hardly commutative!

>Evaluation order is important, and parentheses are the most obvious way of
>expressing it.  Temporary variables are a hack.

Sometimes (many people will break up ten-line expressions for the sake
of clarity).  Nonetheless, there are two problems being solved:
overriding the default groupings, and specifying order of operation.
Any time you use a single solution for two (or more) orthogonal
problems, you have missed out on some potential orthogonality.
(Whether it would in fact be *useful* is a different argument entirely.)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris