newlib-cygwin/newlib/libm/math/w_pow.c

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2000-02-18 03:39:52 +08:00
/* @(#)w_pow.c 5.2 93/10/01 */
/*
* ====================================================
* 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
<<pow>>, <<powf>>---x to the power y
INDEX
pow
INDEX
powf
ANSI_SYNOPSIS
#include <math.h>
double pow(double <[x]>, double <[y]>);
float pow(float <[x]>, float <[y]>);
TRAD_SYNOPSIS
#include <math.h>
double pow(<[x]>, <[y]>);
double <[x]>, <[y]>;
float pow(<[x]>, <[y]>);
float <[x]>, <[y]>;
DESCRIPTION
2003-10-20 Bob Wilson <bob.wilson@acm.org> * libc/locale/locale.c: Use double quotes in code. * libc/locale/locale.tex: Likewise. * libc/libc.texinfo: Hyphenate "floating-point". * libc/machine/necv70/necv70.tex: Likewise. * libc/stdio/sprintf.c: Likewise. * libc/stdio/sscanf.c: Likewise. * libc/stdlib/atof.c: Likewise. * libc/stdlib/ldtoa.c: Fix comment typo. * libc/stdlib/div.c: Use @ifnottex instead of @ifinfo. * libc/stdlib/ldiv.c: Likewise. * libm/common/s_expm1.c: Likewise. * libm/common/s_ilogb.c: Hyphenate "floating-point". Use "nonzero". * libm/common/s_infinity: Hyphenate "double- and single-precision". * libm/common/s_nan.c: Likewise. Also correct the FUNCTION summary. * libm/common/s_nextafter.c: Fix typo. Hyphenate "double-precision" and "floating-point". * libm/common/s_scalbn.c: Correct the FUNCTION summary. * libm/math/e_pow.c: Fix comment typo. * libm/math/math.tex: Hyphenate "single-precision" and "floating-point". * libm/math/s_asinh.c: Use @ifnottex instead of @ifinfo. * libm/math/s_atan.c: Likewise. * libm/math/s_frexp.c: Likewise. Also use "nonzero". * libm/math/s_isnan.c: Hyphenate "single-precision" and "floating-point". Use "nonzero". * libm/math/s_ldexp.c: Use @ifnottex instead of @ifinfo. * libm/math/w_acos.c: Likewise. * libm/math/w_acosh.c: Likewise. * libm/math/w_asin.c: Likewise. * libm/math/w_atan2.c: Likewise. * libm/math/w_atanh.c: Likewise. * libm/math/w_cosh.c: Likewise. * libm/math/w_exp.c: Likewise. * libm/math/w_exp2.c: Likewise. Add missing @end and missing @tex version of 2^x in the description. * libm/math/w_fmod.c: Use @ifnottex instead of @ifinfo. * libm/math/w_gamma.c: Likewise. * libm/math/w_hypot.c: Likewise. * libm/math/w_j0.c: Likewise. * libm/math/w_sinh.c: Likewise. * libm/math/w_pow.c: Replace "exp1.0nt" with "exponent". * libm/mathfp/mathfp.tex: Hyphenate "single-precision" and "floating-point". * libm/mathfp/e_acosh.c: Use @ifnottex instead of @ifinfo. * libm/mathfp/e_atanh.c: Likewise. * libm/mathfp/e_hypot.c: Likewise. * libm/mathfp/er_lgamma.c: Likewise. * libm/mathfp/s_acos.c: Likewise. * libm/mathfp/s_asine.c: Likewise. * libm/mathfp/s_asinh.c: Likewise. * libm/mathfp/s_atan.c: Likewise. * libm/mathfp/s_atan2.c: Likewise. * libm/mathfp/s_atangent.c: Likewise. * libm/mathfp/s_cosh.c: Likewise. * libm/mathfp/s_exp.c: Likewise. * libm/mathfp/s_fmod.c: Likewise. * libm/mathfp/s_frexp.c: Likewise. Also use "nonzero". * libm/mathfp/s_isnan.c: Hyphenate "single-precision" and "floating-point". Use "nonzero". * libm/math/s_pow.c: Replace "exp1.0nt" with "exponent". * libm/mathfp/s_ldexp.c: Use @ifnottex instead of @ifinfo. * libm/mathfp/s_sineh.c: Likewise. * libm/mathfp/w_jn.c: Likewise.
2003-10-21 02:46:38 +08:00
<<pow>> and <<powf>> calculate <[x]> raised to the exponent <[y]>.
2000-02-18 03:39:52 +08:00
@tex
(That is, $x^y$.)
@end tex
RETURNS
On success, <<pow>> and <<powf>> return the value calculated.
When the argument values would produce overflow, <<pow>>
returns <<HUGE_VAL>> and set <<errno>> to <<ERANGE>>. If the
argument <[x]> passed to <<pow>> or <<powf>> is a negative
noninteger, and <[y]> is also not an integer, then <<errno>>
is set to <<EDOM>>. If <[x]> and <[y]> are both 0, then
<<pow>> and <<powf>> return <<1>>.
You can modify error handling for these functions using <<matherr>>.
PORTABILITY
<<pow>> is ANSI C. <<powf>> is an extension. */
/*
* wrapper pow(x,y) return x**y
*/
#include "fdlibm.h"
#include <errno.h>
#ifndef _DOUBLE_IS_32BITS
#ifdef __STDC__
double pow(double x, double y) /* wrapper pow */
#else
double pow(x,y) /* wrapper pow */
double x,y;
#endif
{
#ifdef _IEEE_LIBM
return __ieee754_pow(x,y);
#else
double z;
#ifndef HUGE_VAL
#define HUGE_VAL inf
double inf = 0.0;
SET_HIGH_WORD(inf,0x7ff00000); /* set inf to infinite */
#endif
struct exception exc;
z=__ieee754_pow(x,y);
if(_LIB_VERSION == _IEEE_|| isnan(y)) return z;
if(isnan(x)) {
if(y==0.0) {
/* pow(NaN,0.0) */
/* error only if _LIB_VERSION == _SVID_ & _XOPEN_ */
exc.type = DOMAIN;
exc.name = "pow";
exc.err = 0;
exc.arg1 = x;
exc.arg2 = y;
exc.retval = x;
if (_LIB_VERSION == _IEEE_ ||
_LIB_VERSION == _POSIX_) exc.retval = 1.0;
else if (!matherr(&exc)) {
errno = EDOM;
}
if (exc.err != 0)
errno = exc.err;
return exc.retval;
} else
return z;
}
if(x==0.0){
if(y==0.0) {
/* pow(0.0,0.0) */
/* error only if _LIB_VERSION == _SVID_ */
exc.type = DOMAIN;
exc.name = "pow";
exc.err = 0;
exc.arg1 = x;
exc.arg2 = y;
exc.retval = 0.0;
if (_LIB_VERSION != _SVID_) exc.retval = 1.0;
else if (!matherr(&exc)) {
errno = EDOM;
}
if (exc.err != 0)
errno = exc.err;
return exc.retval;
}
if(finite(y)&&y<0.0) {
/* 0**neg */
exc.type = DOMAIN;
exc.name = "pow";
exc.err = 0;
exc.arg1 = x;
exc.arg2 = y;
if (_LIB_VERSION == _SVID_)
exc.retval = 0.0;
else
exc.retval = -HUGE_VAL;
if (_LIB_VERSION == _POSIX_)
errno = EDOM;
else if (!matherr(&exc)) {
errno = EDOM;
}
if (exc.err != 0)
errno = exc.err;
return exc.retval;
}
return z;
}
if(!finite(z)) {
if(finite(x)&&finite(y)) {
if(isnan(z)) {
/* neg**non-integral */
exc.type = DOMAIN;
exc.name = "pow";
exc.err = 0;
exc.arg1 = x;
exc.arg2 = y;
if (_LIB_VERSION == _SVID_)
exc.retval = 0.0;
else
exc.retval = 0.0/0.0; /* X/Open allow NaN */
if (_LIB_VERSION == _POSIX_)
errno = EDOM;
else if (!matherr(&exc)) {
errno = EDOM;
}
if (exc.err != 0)
errno = exc.err;
return exc.retval;
} else {
/* pow(x,y) overflow */
exc.type = OVERFLOW;
exc.name = "pow";
exc.err = 0;
exc.arg1 = x;
exc.arg2 = y;
if (_LIB_VERSION == _SVID_) {
exc.retval = HUGE;
y *= 0.5;
if(x<0.0&&rint(y)!=y) exc.retval = -HUGE;
} else {
exc.retval = HUGE_VAL;
y *= 0.5;
if(x<0.0&&rint(y)!=y) exc.retval = -HUGE_VAL;
}
if (_LIB_VERSION == _POSIX_)
errno = ERANGE;
else if (!matherr(&exc)) {
errno = ERANGE;
}
if (exc.err != 0)
errno = exc.err;
return exc.retval;
}
}
}
if(z==0.0&&finite(x)&&finite(y)) {
/* pow(x,y) underflow */
exc.type = UNDERFLOW;
exc.name = "pow";
exc.err = 0;
exc.arg1 = x;
exc.arg2 = y;
exc.retval = 0.0;
if (_LIB_VERSION == _POSIX_)
errno = ERANGE;
else if (!matherr(&exc)) {
errno = ERANGE;
}
if (exc.err != 0)
errno = exc.err;
return exc.retval;
}
return z;
#endif
}
#endif /* defined(_DOUBLE_IS_32BITS) */