| |
| /* @(#)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 <<-HUGE_VAL>> 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 = EDOM; |
| } |
| } else { |
| /* log(x<0) */ |
| exc.type = DOMAIN; |
| if (_LIB_VERSION == _POSIX_) |
| errno = EDOM; |
| else if (!matherr(&exc)) { |
| errno = EDOM; |
| } |
| } |
| if (exc.err != 0) |
| errno = exc.err; |
| return exc.retval; |
| #endif |
| } |
| |
| #endif /* defined(_DOUBLE_IS_32BITS) */ |