Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!bionet!agate!eris.berkeley.edu!bowles
From: bowles@eris.berkeley.edu (Jeff A. Bowles)
Newsgroups: comp.lang.c
Subject: Re: doubles used as booleans
Keywords: double,float,boolean
Message-ID: <22352@agate.BERKELEY.EDU>
Date: 30 Mar 89 21:00:08 GMT
References: <8269@xanth.cs.odu.edu>
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Organization: University of California, Berkeley
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In article <8269@xanth.cs.odu.edu> kremer@cs.odu.edu (Lloyd Kremer) writes:
>
>	Can a double be used directly as a boolean?

I don't have a copy of ANSI, but you don't need it for part of the answer:
"Are you really, absolutely sure you wanna compare a floating-point number
to ANYTHING else, just to see if the numbers are EQUAL?"

If you're interested in if a floating-point variable is equal to another
floating-point variable, or if it's equal to zero, well, umm, think very
carefully about whether you're getting ready to shoot yourself in the
foot.

It's the same type of thing that makes 3*(1.0/3.0) not equal to 1.0....

	Jeff Bowles

ps. Comparing to some small amount, like  "abs(x) < 0.00001", doesn't do
a lot better when the calculations are smaller than that, either.