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