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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"; 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.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) */
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