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Portions of this text are reprinted and reproduced in electronic form in the Sun OS Reference Manual, from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between these versions and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html. 8 .\" This notice shall appear on any product containing this material. 9 .\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). 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If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner] 12 .TH log1p 3M "12 Jul 2006" "SunOS 5.11" "Mathematical Library Functions" 13 .SH NAME 14 log1p, log1pf, log1pl \- compute natural logarithm 15 .SH SYNOPSIS 16 .LP 17 .nf 18 c99 [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ] 19 #include <math.h> 20 21 \fBdouble\fR \fBlog1p\fR(\fBdouble\fR \fIx\fR); 22 .fi 23 24 .LP 25 .nf 26 \fBfloat\fR \fBlog1pf\fR(\fBfloat\fR \fIx\fR); 27 .fi 28 29 .LP 30 .nf 31 \fBlong double\fR \fBlog1pl\fR(\fBlong double\fR \fIx\fR); 32 .fi 33 34 .SH DESCRIPTION 35 .sp 36 .LP 37 These functions compute log(e)(1.0 + \fIx\fR). 38 .SH RETURN VALUES 39 .sp 40 .LP 41 Upon successful completion, these functions return the natural logarithm of 1.0 42 + \fIx\fR. 43 .sp 44 .LP 45 If \fIx\fR is \(mi1, a pole error occurs and \fBlog1p()\fR, \fBlog1pf()\fR, and 46 \fBlog1pl()\fR return \(mi\fBHUGE_VAL\fR, \(mi\fBHUGE_VALF\fR, and 47 \(mi\fBHUGE_VALL\fR, respectively. 48 .sp 49 .LP 50 For finite values of \fIx\fR that are less than \(mi1, or if \fIx\fR is 51 \(miInf, a domain error occurs and a NaN is returned. 52 .sp 53 .LP 54 If \fIx\fR is NaN, a NaN is returned. 55 .sp 56 .LP 57 If \fIx\fR is \(+-0 or +Inf, \fIx\fR is returned. 58 .sp 59 .LP 60 For exceptional cases, \fBmatherr\fR(3M) tabulates the values to be returned by 61 \fBlog1p()\fR as specified by SVID3 and XPG3. 62 .SH ERRORS 63 .sp 64 .LP 65 These functions will fail if: 66 .sp 67 .ne 2 68 .mk 69 .na 70 \fBDomain Error\fR 71 .ad 72 .RS 16n 73 .rt 74 The finite value of \fIx\fR is less than \(mi1, or \fIx\fR is -Inf. 75 .sp 76 If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is 77 non-zero, the invalid floating-point exception is raised. 78 .sp 79 The \fBlog1p()\fR function sets \fBerrno\fR to \fBEDOM\fR if the value of 80 \fIx\fR is less than \(mi1. 81 .RE 82 83 .sp 84 .ne 2 85 .mk 86 .na 87 \fBPole Error\fR 88 .ad 89 .RS 16n 90 .rt 91 The value of \fIx\fR is \(mi1. 92 .sp 93 If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is 94 non-zero, the divide-by-zero floating-point exception is raised. 95 .RE 96 97 .SH USAGE 98 .sp 99 .LP 100 An application wanting to check for exceptions should call 101 \fBfeclearexcept\fR(\fBFE_ALL_EXCEPT\fR) before calling these functions. On 102 return, if \fBfetestexcept\fR(\fBFE_INVALID\fR | \fBFE_DIVBYZERO\fR | 103 \fBFE_OVERFLOW\fR | \fBFE_UNDERFLOW\fR) is non-zero, an exception has been 104 raised. An application should either examine the return value or check the 105 floating point exception flags to detect exceptions. 106 .sp 107 .LP 108 An application can also set \fBerrno\fR to 0 before calling \fBlog1p()\fR. On 109 return, if \fBerrno\fR is non-zero, an error has occurred. The \fBlog1pf()\fR 110 and \fBlog1pl()\fR functions do not set \fBerrno\fR. 111 .SH ATTRIBUTES 112 .sp 113 .LP 114 See \fBattributes\fR(5) for descriptions of the following attributes: 115 .sp 116 117 .sp 118 .TS 119 tab() box; 120 cw(2.75i) |cw(2.75i) 121 lw(2.75i) |lw(2.75i) 122 . 123 ATTRIBUTE TYPEATTRIBUTE VALUE 124 _ 125 Interface StabilityStandard 126 _ 127 MT-LevelMT-Safe 128 .TE 129 130 .SH SEE ALSO 131 .sp 132 .LP 133 \fBfeclearexcept\fR(3M), \fBfetestexcept\fR(3M), \fBlog\fR(3M), 134 \fBmath.h\fR(3HEAD), \fBmatherr\fR(3M), \fBattributes\fR(5), \fBstandards\fR(5)