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[/] [openrisc/] [trunk/] [gnu-old/] [newlib-1.17.0/] [newlib/] [libm/] [math/] [w_log.c] - Rev 816
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/* @(#)w_log.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 <<log>>, <<logf>>---natural logarithms INDEX log INDEX logf ANSI_SYNOPSIS #include <math.h> double log(double <[x]>); float logf(float <[x]>); TRAD_SYNOPSIS #include <math.h> double log(<[x]>); double <[x]>; float logf(<[x]>); float <[x]>; DESCRIPTION Return the natural logarithm of <[x]>, that is, its logarithm base e (where e is the base of the natural system of logarithms, 2.71828@dots{}). <<log>> and <<logf>> are identical save for the return and argument types. You can use the (non-ANSI) function <<matherr>> to specify error handling for these functions. RETURNS Normally, returns the calculated value. When <[x]> is zero, the returned value is <<-HUGE_VAL>> and <<errno>> is set to <<ERANGE>>. When <[x]> is negative, the returned value is NaN (not a number) and <<errno>> is set to <<EDOM>>. You can control the error behavior via <<matherr>>. PORTABILITY <<log>> is ANSI. <<logf>> is an extension. */ /* * wrapper log(x) */ #include "fdlibm.h" #include <errno.h> #ifndef _DOUBLE_IS_32BITS #ifdef __STDC__ double log(double x) /* wrapper log */ #else double log(x) /* wrapper log */ double x; #endif { #ifdef _IEEE_LIBM return __ieee754_log(x); #else double z; struct exception exc; z = __ieee754_log(x); if(_LIB_VERSION == _IEEE_ || isnan(x) || x > 0.0) return z; #ifndef HUGE_VAL #define HUGE_VAL inf double inf = 0.0; SET_HIGH_WORD(inf,0x7ff00000); /* set inf to infinite */ #endif exc.name = "log"; exc.err = 0; exc.arg1 = x; exc.arg2 = x; if (_LIB_VERSION == _SVID_) exc.retval = -HUGE; else exc.retval = -HUGE_VAL; if(x==0.0) { /* log(0) */ exc.type = SING; if (_LIB_VERSION == _POSIX_) errno = ERANGE; else if (!matherr(&exc)) { errno = ERANGE; } } else { /* log(x<0) */ exc.type = DOMAIN; if (_LIB_VERSION == _POSIX_) errno = EDOM; else if (!matherr(&exc)) { errno = EDOM; } exc.retval = nan(""); } if (exc.err != 0) errno = exc.err; return exc.retval; #endif } #endif /* defined(_DOUBLE_IS_32BITS) */