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From: merlyn@starfire.UUCP (Brian Westley)
Newsgroups: comp.lang.c
Subject: + != + (floating point)
Message-ID: <133@starfire.UUCP>
Date: Mon, 20-Apr-87 23:37:50 EST
Article-I.D.: starfire.133
Posted: Mon Apr 20 23:37:50 1987
Date-Received: Thu, 23-Apr-87 04:57:05 EST
Organization: Starfire Consultings Services, Mpls., MN
Lines: 26
Summary: int + int != float + float


Adding my $.02 about this whole order of evaluation to-do;

1) C allows the compiler to rearrange expressions involving communative &
associative operators (+*^&| etc)

2) C, unfortunately, lumped both kinds of + together (integer add, float add).
Integer addition is communative & associative.  Floating addition is
communative, but NOT associative.  C 'defines' it to be something it isn't.
I would prefer a compiler that doesn't perform associative transformations
with operators that aren't associative.  (For all you people about to yell
"parentheses affect precidence, not order of evaluation", just consider
(a%b)%c vs. a%(b%c) - if the %'s were +'s, the expression can be rearranged,
but as written, it cannot, since % isn't associative or communative).

3) Does the proposed standard consider floating + to be associative?
I hope it doesn't, since it isn't, C history notwithstanding.  It probably
does, though.  +(We must be upward compatible with past errors).

4) Of course, (f1 + f2 + f3) should be rearrange-able, simple left-to-right
associativity should be 'weaker'.

5) The same holds for most floating operations.

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Merlyn Leroy ..rutgers!dayton!rosevax!rose3!starfire!merlyn