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/* @(#)s_isnan.c 5.1 93/09/24 */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/*
FUNCTION
<<fpclassify>>, <<isfinite>>, <<isinf>>, <<isnan>>, and <<isnormal>>--floating-point classification macros; <<finite>>, <<finitef>>, <<isinf>>, <<isinff>>, <<isnan>>, <<isnanf>>--test for exceptional numbers
@c C99 (start
INDEX
fpclassify
INDEX
isfinite
INDEX
isinf
INDEX
isnan
INDEX
isnormal
@c C99 end)
@c SUSv2 (start
INDEX
isnan
INDEX
isinf
INDEX
finite
INDEX
isnanf
INDEX
isinff
INDEX
finitef
@c SUSv2 end)
ANSI_SYNOPSIS
[C99 standard macros:]
#include <math.h>
int fpclassify(real-floating <[x]>);
int isfinite(real-floating <[x]>);
int isinf(real-floating <[x]>);
int isnan(real-floating <[x]>);
int isnormal(real-floating <[x]>);
[Archaic SUSv2 functions:]
#include <ieeefp.h>
int isnan(double <[arg]>);
int isinf(double <[arg]>);
int finite(double <[arg]>);
int isnanf(float <[arg]>);
int isinff(float <[arg]>);
int finitef(float <[arg]>);
DESCRIPTION
<<fpclassify>>, <<isfinite>>, <<isinf>>, <<isnan>>, and <<isnormal>> are macros
defined for use in classifying floating-point numbers. This is a help because
of special "values" like NaN and infinities. In the synopses shown,
"real-floating" indicates that the argument is an expression of real floating
type. These function-like macros are C99 and POSIX-compliant, and should be
used instead of the now-archaic SUSv2 functions.
The <<fpclassify>> macro classifies its argument value as NaN, infinite, normal,
subnormal, zero, or into another implementation-defined category. First, an
argument represented in a format wider than its semantic type is converted to
its semantic type. Then classification is based on the type of the argument.
The <<fpclassify>> macro returns the value of the number classification macro
appropriate to the value of its argument:
o+
o FP_INFINITE
<[x]> is either plus or minus infinity;
o FP_NAN
<[x]> is "Not A Number" (plus or minus);
o FP_NORMAL
<[x]> is a "normal" number (i.e. is none of the other special forms);
o FP_SUBNORMAL
<[x]> is too small be stored as a regular normalized number (i.e. loss of precision is likely); or
o FP_ZERO
<[x]> is 0 (either plus or minus).
o-
The "<<is>>" set of macros provide a useful set of shorthand ways for
classifying floating-point numbers, providing the following equivalent
relations:
o+
o <<isfinite>>(<[x]>)
returns non-zero if <[x]> is finite. (It is equivalent to
(<<fpclassify>>(<[x]>) != FP_INFINITE && <<fpclassify>>(<[x]>) != FP_NAN).)
o <<isinf>>(<[x]>)
returns non-zero if <[x]> is infinite. (It is equivalent to
(<<fpclassify>>(<[x]>) == FP_INFINITE).)
o <<isnan>>(<[x]>)
returns non-zero if <[x]> is NaN. (It is equivalent to
(<<fpclassify>>(<[x]>) == FP_NAN).)
o <<isnormal>>(<[x]>)
returns non-zero if <[x]> is normal. (It is equivalent to
(<<fpclassify>>(<[x]>) == FP_NORMAL).)
o-
The archaic SUSv2 functions provide information on the floating-point
argument supplied.
There are five major number formats ("exponent" referring to the
biased exponent in the binary-encoded number):
o+
o zero
A number which contains all zero bits, excluding the sign bit.
o subnormal
A number with a zero exponent but a nonzero fraction.
o normal
A number with an exponent and a fraction.
o infinity
A number with an all 1's exponent and a zero fraction.
o NAN
A number with an all 1's exponent and a nonzero fraction.
o-
<<isnan>> returns 1 if the argument is a nan. <<isinf>>
returns 1 if the argument is infinity. <<finite>> returns 1 if the
argument is zero, subnormal or normal.
The <<isnanf>>, <<isinff>> and <<finitef>> functions perform the same
operations as their <<isnan>>, <<isinf>> and <<finite>>
counterparts, but on single-precision floating-point numbers.
It should be noted that the C99 standard dictates that <<isnan>>
and <<isinf>> are macros that operate on multiple types of
floating-point. The SUSv2 standard declares <<isnan>> as
a function taking double. Newlib has decided to declare
them both as macros in math.h and as functions in ieeefp.h to
maintain backward compatibility.
RETURNS
@comment Formatting note: "$@" forces a new line
The fpclassify macro returns the value corresponding to the appropriate FP_ macro.@*
The isfinite macro returns nonzero if <[x]> is finite, else 0.@*
The isinf macro returns nonzero if <[x]> is infinite, else 0.@*
The isnan macro returns nonzero if <[x]> is an NaN, else 0.@*
The isnormal macro returns nonzero if <[x]> has a normal value, else 0.
PORTABILITY
math.h macros are C99, POSIX.
ieeefp.h funtions are outdated and should be avoided.
QUICKREF
isnan - pure
QUICKREF
isinf - pure
QUICKREF
finite - pure
QUICKREF
isnan - pure
QUICKREF
isinf - pure
QUICKREF
finite - pure
*/
/*
* isnan(x) returns 1 is x is nan, else 0;
* no branching!
*
* The C99 standard dictates that isnan is a macro taking
* multiple floating-point types while the SUSv2 standard
* notes it is a function taking a double argument. Newlib
* has chosen to implement it as a macro in <math.h> and
* declare it as a function in <ieeefp.h>.
*/
#include "fdlibm.h"
#include <ieeefp.h>
#ifndef _DOUBLE_IS_32BITS
#ifdef __STDC__
int isnan(double x)
#else
int isnan(x)
double x;
#endif
{
__int32_t hx,lx;
EXTRACT_WORDS(hx,lx,x);
hx &= 0x7fffffff;
hx |= (__uint32_t)(lx|(-lx))>>31;
hx = 0x7ff00000 - hx;
return (int)(((__uint32_t)(hx))>>31);
}
#endif /* _DOUBLE_IS_32BITS */
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