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Path: utzoo!utgpu!utcsri!flaps
From: flaps@utcsri.UUCP
Newsgroups: comp.lang.c
Subject: Re: Optimizing Floating-Point Expression Evaluation
Message-ID: <4616@utcsri.UUCP>
Date: Sat, 18-Apr-87 17:43:39 EST
Article-I.D.: utcsri.4616
Posted: Sat Apr 18 17:43:39 1987
Date-Received: Sun, 19-Apr-87 00:34:06 EST
References: <16646@sun.uucp>
Reply-To: flaps@utcsri.UUCP (Alan J Rosenthal)
Organization: University of Toronto
Lines: 27
Keywords: float point expression
Summary: 


David Hough writes that if you say "(a + b) + c" you mean for the evaluation
to be done in that order, and if you don't care you will say "a + b + c".
That's fine, but please explain how you can know whether or not I care about
evaluation order in the following:

	#define THING (a + 3.5)

	...

	c = (THING + 1.1) * 2.6;


How do I say that I want the 3.5 and 1.1 to be added at compile time?
Assuming I say this by #defining THING as "a + 3.5" (which is bug-causing
practice, by the way), the bigger question is how do I get you to
multiply the 2.6 into the parentheses to compile as "c = (a*2.6) + 11.96"?

-- 

Alan J Rosenthal

flaps@csri.toronto.edu, {seismo!utai or utzoo}!utcsri!flaps,
flaps@toronto on csnet, flaps at utorgpu on bitnet.

"Probably the best operating system in the world is the [operating system]
made for the PDP-11 by Bell Laboratories." - Ted Nelson, October 1977