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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 logb 3M "12 Jul 2006" "SunOS 5.11" "Mathematical Library Functions" 13 .SH NAME 14 logb, logbf, logbl \- radix-independent exponent 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 \fBlogb\fR(\fBdouble\fR \fIx\fR); 22 .fi 23 24 .LP 25 .nf 26 \fBfloat\fR \fBlogbf\fR(\fBfloat\fR \fIx\fR); 27 .fi 28 29 .LP 30 .nf 31 \fBlong double\fR \fBlogbl\fR(\fBlong double\fR \fIx\fR); 32 .fi 33 34 .LP 35 .nf 36 cc [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ] 37 #include <math.h> 38 39 \fBdouble\fR \fBlogb\fR(\fBdouble\fR \fIx\fR); 40 .fi 41 42 .LP 43 .nf 44 \fBfloat\fR \fBlogbf\fR(\fBfloat\fR \fIx\fR); 45 .fi 46 47 .LP 48 .nf 49 \fBlong double\fR \fBlogbl\fR(\fBlong double\fR \fIx\fR); 50 .fi 51 52 .SH DESCRIPTION 53 .sp 54 .LP 55 These functions compute the exponent of \fIx\fR, which is the integral part of 56 log(\fIr\fR) |\fIx\fR|, as a signed floating point value, for non-zero \fIx\fR, 57 where \fIr\fR is the radix of the machine's floating-point arithmetic, which is 58 the value of \fBFLT_RADIX\fR defined in the <\fBfloat.h\fR> header. 59 .SH RETURN VALUES 60 .sp 61 .LP 62 Upon successful completion, these functions return the exponent of \fIx\fR. 63 .sp 64 .LP 65 If \fIx\fR is subnormal: 66 .RS +4 67 .TP 68 .ie t \(bu 69 .el o 70 For SUSv3-conforming applications compiled with the \fBc99\fR compiler driver 71 (see \fBstandards\fR(5)), the exponent of \fIx\fR as if \fIx\fR were normalized 72 is returned. 73 .RE 74 .RS +4 75 .TP 76 .ie t \(bu 77 .el o 78 Otherwise, if compiled with the \fBcc\fR compiler driver, \(mi1022, \(mi126, 79 and \(mi16382 are returned for \fBlogb()\fR, \fBlogbf()\fR, and \fBlogbl()\fR, 80 respectively. 81 .RE 82 .sp 83 .LP 84 If \fIx\fR is \(+-0, a pole error occurs and \fBlogb()\fR, \fBlogbf()\fR, and 85 \fBlogbl()\fR return \(mi\fBHUGE_VAL\fR, \(mi\fBHUGE_VALF\fR, and 86 \(mi\fBHUGE_VALL\fR, respectively. 87 .sp 88 .LP 89 If \fIx\fR is NaN, a NaN is returned. 90 .sp 91 .LP 92 If \fIx\fR is \(+-Inf, +Inf is returned. 93 .SH ERRORS 94 .sp 95 .LP 96 These functions will fail if: 97 .sp 98 .ne 2 99 .mk 100 .na 101 \fBPole Error\fR 102 .ad 103 .RS 14n 104 .rt 105 The value of \fIx\fR is \(+-0. 106 .sp 107 If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is 108 non-zero, the divide-by-zero floating-point exception is raised. 109 .sp 110 The \fBlogb()\fR function sets \fBerrno\fR to \fBEDOM\fR if the value of 111 \fIx\fR is 0. 112 .RE 113 114 .SH USAGE 115 .sp 116 .LP 117 An application wanting to check for exceptions should call 118 \fBfeclearexcept\fR(\fBFE_ALL_EXCEPT\fR) before calling these functions. On 119 return, if \fBfetestexcept\fR(\fBFE_INVALID\fR | \fBFE_DIVBYZERO\fR | 120 \fBFE_OVERFLOW\fR | \fBFE_UNDERFLOW\fR) is non-zero, an exception has been 121 raised. An application should either examine the return value or check the 122 floating point exception flags to detect exceptions. 123 .sp 124 .LP 125 An application can also set \fBerrno\fR to 0 before calling \fBlogb()\fR. On 126 return, if \fBerrno\fR is non-zero, an error has occurred. The \fBlogbf()\fR 127 and \fBlogbl()\fR functions do not set \fBerrno\fR. 128 .SH ATTRIBUTES 129 .sp 130 .LP 131 See \fBattributes\fR(5) for descriptions of the following attributes: 132 .sp 133 134 .sp 135 .TS 136 tab() box; 137 cw(2.75i) |cw(2.75i) 138 lw(2.75i) |lw(2.75i) 139 . 140 ATTRIBUTE TYPEATTRIBUTE VALUE 141 _ 142 Interface StabilityStandard 143 _ 144 MT-LevelMT-Safe 145 .TE 146 147 .SH SEE ALSO 148 .sp 149 .LP 150 \fBfeclearexcept\fR(3M), \fBfetestexcept\fR(3M), \fBilogb\fR(3M), 151 \fBmath.h\fR(3HEAD), \fBmatherr\fR(3M), \fBscalb\fR(3M), \fBattributes\fR(5), 152 \fBstandards\fR(5)