[444] | 1 | |
---|
| 2 | /* @(#)w_log.c 5.1 93/09/24 */ |
---|
| 3 | /* |
---|
| 4 | * ==================================================== |
---|
| 5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
---|
| 6 | * |
---|
| 7 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
---|
| 8 | * Permission to use, copy, modify, and distribute this |
---|
| 9 | * software is freely granted, provided that this notice |
---|
| 10 | * is preserved. |
---|
| 11 | * ==================================================== |
---|
| 12 | */ |
---|
| 13 | |
---|
| 14 | /* |
---|
| 15 | FUNCTION |
---|
| 16 | <<log>>, <<logf>>---natural logarithms |
---|
| 17 | |
---|
| 18 | INDEX |
---|
| 19 | log |
---|
| 20 | INDEX |
---|
| 21 | logf |
---|
| 22 | |
---|
| 23 | SYNOPSIS |
---|
| 24 | #include <math.h> |
---|
| 25 | double log(double <[x]>); |
---|
| 26 | float logf(float <[x]>); |
---|
| 27 | |
---|
| 28 | DESCRIPTION |
---|
| 29 | Return the natural logarithm of <[x]>, that is, its logarithm base e |
---|
| 30 | (where e is the base of the natural system of logarithms, 2.71828@dots{}). |
---|
| 31 | <<log>> and <<logf>> are identical save for the return and argument types. |
---|
| 32 | |
---|
| 33 | You can use the (non-ANSI) function <<matherr>> to specify error |
---|
| 34 | handling for these functions. |
---|
| 35 | |
---|
| 36 | RETURNS |
---|
| 37 | Normally, returns the calculated value. When <[x]> is zero, the |
---|
| 38 | returned value is <<-HUGE_VAL>> and <<errno>> is set to <<ERANGE>>. |
---|
| 39 | When <[x]> is negative, the returned value is NaN (not a number) and |
---|
| 40 | <<errno>> is set to <<EDOM>>. You can control the error behavior via |
---|
| 41 | <<matherr>>. |
---|
| 42 | |
---|
| 43 | PORTABILITY |
---|
| 44 | <<log>> is ANSI. <<logf>> is an extension. |
---|
| 45 | */ |
---|
| 46 | |
---|
| 47 | /* |
---|
| 48 | * wrapper log(x) |
---|
| 49 | */ |
---|
| 50 | |
---|
| 51 | #include "fdlibm.h" |
---|
| 52 | #include <errno.h> |
---|
| 53 | |
---|
| 54 | #ifndef _DOUBLE_IS_32BITS |
---|
| 55 | |
---|
| 56 | #ifdef __STDC__ |
---|
| 57 | double log(double x) /* wrapper log */ |
---|
| 58 | #else |
---|
| 59 | double log(x) /* wrapper log */ |
---|
| 60 | double x; |
---|
| 61 | #endif |
---|
| 62 | { |
---|
| 63 | #ifdef _IEEE_LIBM |
---|
| 64 | return __ieee754_log(x); |
---|
| 65 | #else |
---|
| 66 | double z; |
---|
| 67 | struct exception exc; |
---|
| 68 | z = __ieee754_log(x); |
---|
| 69 | if(_LIB_VERSION == _IEEE_ || isnan(x) || x > 0.0) return z; |
---|
| 70 | #ifndef HUGE_VAL |
---|
| 71 | #define HUGE_VAL inf |
---|
| 72 | double inf = 0.0; |
---|
| 73 | |
---|
| 74 | SET_HIGH_WORD(inf,0x7ff00000); /* set inf to infinite */ |
---|
| 75 | #endif |
---|
| 76 | exc.name = "log"; |
---|
| 77 | exc.err = 0; |
---|
| 78 | exc.arg1 = x; |
---|
| 79 | exc.arg2 = x; |
---|
| 80 | if (_LIB_VERSION == _SVID_) |
---|
| 81 | exc.retval = -HUGE; |
---|
| 82 | else |
---|
| 83 | exc.retval = -HUGE_VAL; |
---|
| 84 | if(x==0.0) { |
---|
| 85 | /* log(0) */ |
---|
| 86 | exc.type = SING; |
---|
| 87 | if (_LIB_VERSION == _POSIX_) |
---|
| 88 | errno = ERANGE; |
---|
| 89 | else if (!matherr(&exc)) { |
---|
| 90 | errno = ERANGE; |
---|
| 91 | } |
---|
| 92 | } else { |
---|
| 93 | /* log(x<0) */ |
---|
| 94 | exc.type = DOMAIN; |
---|
| 95 | if (_LIB_VERSION == _POSIX_) |
---|
| 96 | errno = EDOM; |
---|
| 97 | else if (!matherr(&exc)) { |
---|
| 98 | errno = EDOM; |
---|
| 99 | } |
---|
| 100 | exc.retval = nan(""); |
---|
| 101 | } |
---|
| 102 | if (exc.err != 0) |
---|
| 103 | errno = exc.err; |
---|
| 104 | return exc.retval; |
---|
| 105 | #endif |
---|
| 106 | } |
---|
| 107 | |
---|
| 108 | #endif /* defined(_DOUBLE_IS_32BITS) */ |
---|