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From: ken@turtlevax.UUCP (Ken Turkowski)
Newsgroups: net.lang.c
Subject: How to test for +/- INFINITY, etc. in C with IEEE
Message-ID: <993@turtlevax.UUCP>
Date: Tue, 10-Dec-85 23:46:27 EST
Article-I.D.: turtleva.993
Posted: Tue Dec 10 23:46:27 1985
Date-Received: Fri, 13-Dec-85 08:06:03 EST
Organization: CIMLINC, Inc. @ Menlo Park, CA
Lines: 26
Keywords: conversions are a pain in casts
Summary: 0x1050 is a bit pattern, not an integer

I would like to be able to test for INFINITY, NaN, and other such
things within C.  Now, if I try to cast the value for INFINITY
(0x7F800000 in single) to a float,

	((float)(0x7F800000))

the C compiler changes it into 0x4EFF0000 which does not compare the
same as 0x7F800000.

Can anyone recommend a way to quickly compare a float against
INFINITY?  I can't use a subroutine, because the C compiler changes the
float to a double.

*STEAM follows*

The C compiler should assume that only decimal constants need be
converted from integer to floating point.

Octal and hexadecimal constants are used to represent bit patterns, not
numbers.  There is no reason that the compiler should assume that a
particular bit pattern represents an integer rather than a
floating-point number or something even more exotic.
-- 
Ken Turkowski @ CIMLINC, Menlo Park, CA
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