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 ANSI_SYNOPSIS 24 #include <math.h> 25 double log(double <[x]>); 26 float logf(float <[x]>); 27 28 TRAD_SYNOPSIS 29 #include <math.h> 30 double log(<[x]>); 31 double <[x]>; 32 33 float logf(<[x]>); 34 float <[x]>; 35 36 DESCRIPTION 37 Return the natural logarithm of <[x]>, that is, its logarithm base e 38 (where e is the base of the natural system of logarithms, 2.71828@dots{}). 39 <<log>> and <<logf>> are identical save for the return and argument types. 40 41 You can use the (non-ANSI) function <<matherr>> to specify error 42 handling for these functions. 43 44 RETURNS 45 Normally, returns the calculated value. When <[x]> is zero, the 46 returned value is <<-HUGE_VAL>> and <<errno>> is set to <<ERANGE>>. 47 When <[x]> is negative, the returned value is <<-HUGE_VAL>> and 48 <<errno>> is set to <<EDOM>>. You can control the error behavior via 49 <<matherr>>. 50 51 PORTABILITY 52 <<log>> is ANSI, <<logf>> is an extension. 53 */ 54 55 /* 56 * wrapper log(x) 57 */ 58 59 #include "fdlibm.h" 60 #include <errno.h> 61 62 #ifndef _DOUBLE_IS_32BITS 63 64 #ifdef __STDC__ log(double x)65 double log(double x) /* wrapper log */ 66 #else 67 double log(x) /* wrapper log */ 68 double x; 69 #endif 70 { 71 #ifdef _IEEE_LIBM 72 return __ieee754_log(x); 73 #else 74 double z; 75 struct exception exc; 76 z = __ieee754_log(x); 77 if(_LIB_VERSION == _IEEE_ || isnan(x) || x > 0.0) return z; 78 #ifndef HUGE_VAL 79 #define HUGE_VAL inf 80 double inf = 0.0; 81 82 SET_HIGH_WORD(inf,0x7ff00000); /* set inf to infinite */ 83 #endif 84 exc.name = "log"; 85 exc.err = 0; 86 exc.arg1 = x; 87 exc.arg2 = x; 88 if (_LIB_VERSION == _SVID_) 89 exc.retval = -HUGE; 90 else 91 exc.retval = -HUGE_VAL; 92 if(x==0.0) { 93 /* log(0) */ 94 exc.type = SING; 95 if (_LIB_VERSION == _POSIX_) 96 errno = ERANGE; 97 else if (!matherr(&exc)) { 98 errno = EDOM; 99 } 100 } else { 101 /* log(x<0) */ 102 exc.type = DOMAIN; 103 if (_LIB_VERSION == _POSIX_) 104 errno = EDOM; 105 else if (!matherr(&exc)) { 106 errno = EDOM; 107 } 108 } 109 if (exc.err != 0) 110 errno = exc.err; 111 return exc.retval; 112 #endif 113 } 114 115 #endif /* defined(_DOUBLE_IS_32BITS) */ 116