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/* @(#)w_exp.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

        <<exp>>, <<expf>>---exponential

INDEX

        exp

INDEX

        expf

ANSI_SYNOPSIS

        #include <math.h>

        double exp(double <[x]>);

        float expf(float <[x]>);

TRAD_SYNOPSIS

        #include <math.h>

        double exp(<[x]>);

        double <[x]>;

        float expf(<[x]>);

        float <[x]>;

DESCRIPTION

        <<exp>> and <<expf>> calculate the exponential of <[x]>, that is,

        @ifinfo

        e raised to the power <[x]> (where e

        @end ifinfo

        @tex

        $e^x$ (where $e$

        @end tex

        is the base of the natural system of logarithms, approximately 2.71828).

        You can use the (non-ANSI) function <<matherr>> to specify

        error handling for these functions.

RETURNS

        On success, <<exp>> and <<expf>> return the calculated value.

        If the result underflows, the returned value is <<0>>.  If the

        result overflows, the returned value is <<HUGE_VAL>>.  In

        either case, <<errno>> is set to <<ERANGE>>.

PORTABILITY

        <<exp>> is ANSI C.  <<expf>> is an extension.

*/

/*

 * wrapper exp(x)

 */

#include "fdlibm.h"

#include <errno.h>

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__

static const double

#else

static double

#endif

o_threshold=  7.09782712893383973096e+02,  /* 0x40862E42, 0xFEFA39EF */

u_threshold= -7.45133219101941108420e+02;  /* 0xc0874910, 0xD52D3051 */

#ifdef __STDC__

        double exp(double x)            /* wrapper exp */

#else

        double exp(x)                   /* wrapper exp */

        double x;

#endif

{

#ifdef _IEEE_LIBM

        return __ieee754_exp(x);

#else

        double z;

        struct exception exc;

        z = __ieee754_exp(x);

        if(_LIB_VERSION == _IEEE_) return z;

        if(finite(x)) {

            if(x>o_threshold) {

                /* exp(finite) overflow */

#ifndef HUGE_VAL

#define HUGE_VAL inf

                double inf = 0.0;

                SET_HIGH_WORD(inf,0x7ff00000);  /* set inf to infinite */

#endif

                exc.type = OVERFLOW;

                exc.name = "exp";

                exc.err = 0;

                exc.arg1 = exc.arg2 = x;

                if (_LIB_VERSION == _SVID_)

                  exc.retval = HUGE;

                else

                  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;

            } else if(x<u_threshold) {

                /* exp(finite) underflow */

                exc.type = UNDERFLOW;

                exc.name = "exp";

                exc.err = 0;

                exc.arg1 = exc.arg2 = x;

                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) */