137 lines
2.8 KiB
C
137 lines
2.8 KiB
C
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/* @(#)w_exp.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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<<exp>>, <<expf>>---exponential
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INDEX
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exp
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INDEX
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expf
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ANSI_SYNOPSIS
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#include <math.h>
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double exp(double <[x]>);
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float expf(float <[x]>);
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TRAD_SYNOPSIS
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#include <math.h>
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double exp(<[x]>);
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double <[x]>;
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float expf(<[x]>);
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float <[x]>;
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DESCRIPTION
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<<exp>> and <<expf>> calculate the exponential of <[x]>, that is,
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@ifnottex
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e raised to the power <[x]> (where e
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@end ifnottex
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@tex
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$e^x$ (where $e$
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@end tex
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is the base of the natural system of logarithms, approximately 2.71828).
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You can use the (non-ANSI) function <<matherr>> to specify
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error handling for these functions.
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RETURNS
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On success, <<exp>> and <<expf>> return the calculated value.
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If the result underflows, the returned value is <<0>>. If the
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result overflows, the returned value is <<HUGE_VAL>>. In
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either case, <<errno>> is set to <<ERANGE>>.
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PORTABILITY
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<<exp>> is ANSI C. <<expf>> is an extension.
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*/
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/*
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* wrapper exp(x)
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*/
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#include "fdlibm.h"
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#include <errno.h>
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#ifndef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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static const double
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#else
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static double
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#endif
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o_threshold= 7.09782712893383973096e+02, /* 0x40862E42, 0xFEFA39EF */
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u_threshold= -7.45133219101941108420e+02; /* 0xc0874910, 0xD52D3051 */
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#ifdef __STDC__
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double exp(double x) /* wrapper exp */
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#else
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double exp(x) /* wrapper exp */
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double x;
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#endif
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{
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#ifdef _IEEE_LIBM
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return __ieee754_exp(x);
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#else
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double z;
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struct exception exc;
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z = __ieee754_exp(x);
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if(_LIB_VERSION == _IEEE_) return z;
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if(finite(x)) {
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if(x>o_threshold) {
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/* exp(finite) overflow */
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#ifndef HUGE_VAL
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#define HUGE_VAL inf
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double inf = 0.0;
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SET_HIGH_WORD(inf,0x7ff00000); /* set inf to infinite */
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#endif
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exc.type = OVERFLOW;
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exc.name = "exp";
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exc.err = 0;
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exc.arg1 = exc.arg2 = x;
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if (_LIB_VERSION == _SVID_)
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exc.retval = HUGE;
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else
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exc.retval = HUGE_VAL;
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if (_LIB_VERSION == _POSIX_)
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errno = ERANGE;
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else if (!matherr(&exc)) {
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errno = ERANGE;
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}
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if (exc.err != 0)
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errno = exc.err;
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return exc.retval;
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} else if(x<u_threshold) {
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/* exp(finite) underflow */
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exc.type = UNDERFLOW;
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exc.name = "exp";
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exc.err = 0;
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exc.arg1 = exc.arg2 = x;
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exc.retval = 0.0;
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if (_LIB_VERSION == _POSIX_)
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errno = ERANGE;
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else if (!matherr(&exc)) {
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errno = ERANGE;
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}
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if (exc.err != 0)
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errno = exc.err;
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return exc.retval;
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}
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}
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return z;
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#endif
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}
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#endif /* defined(_DOUBLE_IS_32BITS) */
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