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