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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 | ANSI_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 | TRAD_SYNOPSIS
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| 29 | #include <math.h>
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| 30 | double log(<[x]>);
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| 31 | double <[x]>;
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| 32 |
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| 33 | float logf(<[x]>);
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| 34 | float <[x]>;
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| 35 |
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| 36 | DESCRIPTION
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| 37 | Return the natural logarithm of <[x]>, that is, its logarithm base e
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| 38 | (where e is the base of the natural system of logarithms, 2.71828@dots{}).
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| 39 | <<log>> and <<logf>> are identical save for the return and argument types.
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| 40 |
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| 41 | You can use the (non-ANSI) function <<matherr>> to specify error
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| 42 | handling for these functions.
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| 43 |
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| 44 | RETURNS
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| 45 | Normally, returns the calculated value. When <[x]> is zero, the
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| 46 | returned value is <<-HUGE_VAL>> and <<errno>> is set to <<ERANGE>>.
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| 47 | When <[x]> is negative, the returned value is <<-HUGE_VAL>> and
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| 48 | <<errno>> is set to <<EDOM>>. You can control the error behavior via
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| 49 | <<matherr>>.
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| 50 |
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| 51 | PORTABILITY
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| 52 | <<log>> is ANSI, <<logf>> is an extension.
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| 53 | */
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| 54 |
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| 55 | /*
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| 56 | * wrapper log(x)
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| 57 | */
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| 58 |
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| 59 | #include "fdlibm.h"
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| 60 | #include <errno.h>
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| 61 |
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| 62 | #ifndef _DOUBLE_IS_32BITS
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| 63 |
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| 64 | #ifdef __STDC__
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| 65 | double log(double x) /* wrapper log */
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| 66 | #else
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| 67 | double log(x) /* wrapper log */
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| 68 | double x;
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| 69 | #endif
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| 70 | {
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| 71 | #ifdef _IEEE_LIBM
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| 72 | return __ieee754_log(x);
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| 73 | #else
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| 74 | double z;
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| 75 | struct exception exc;
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| 76 | z = __ieee754_log(x);
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| 77 | if(_LIB_VERSION == _IEEE_ || isnan(x) || x > 0.0) return z;
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| 78 | #ifndef HUGE_VAL
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| 79 | #define HUGE_VAL inf
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| 80 | double inf = 0.0;
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| 81 |
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| 82 | SET_HIGH_WORD(inf,0x7ff00000); /* set inf to infinite */
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| 83 | #endif
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| 84 | exc.name = "log";
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| 85 | exc.err = 0;
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| 86 | exc.arg1 = x;
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| 87 | exc.arg2 = x;
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| 88 | if (_LIB_VERSION == _SVID_)
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| 89 | exc.retval = -HUGE;
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| 90 | else
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| 91 | exc.retval = -HUGE_VAL;
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| 92 | if(x==0.0) {
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| 93 | /* log(0) */
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| 94 | exc.type = SING;
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| 95 | if (_LIB_VERSION == _POSIX_)
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| 96 | errno = ERANGE;
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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 | } else {
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| 101 | /* log(x<0) */
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| 102 | exc.type = DOMAIN;
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| 103 | if (_LIB_VERSION == _POSIX_)
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| 104 | errno = EDOM;
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| 105 | else if (!matherr(&exc)) {
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| 106 | errno = EDOM;
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| 107 | }
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| 108 | }
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| 109 | if (exc.err != 0)
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| 110 | errno = exc.err;
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| 111 | return exc.retval;
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| 112 | #endif
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| 113 | }
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| 114 |
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| 115 | #endif /* defined(_DOUBLE_IS_32BITS) */
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