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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, |
| @ifnottex |
| e raised to the power <[x]> (where e |
| @end ifnottex |
| @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) */ |