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fea681da | 1 | .\" Copyright 2004 Andries Brouwer <aeb@cwi.nl>. |
d33cd73d MK |
2 | .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk |
3 | .\" <mtk.manpages@gmail.com> | |
fea681da | 4 | .\" |
93015253 | 5 | .\" %%%LICENSE_START(VERBATIM) |
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6 | .\" Permission is granted to make and distribute verbatim copies of this |
7 | .\" manual provided the copyright notice and this permission notice are | |
8 | .\" preserved on all copies. | |
9 | .\" | |
10 | .\" Permission is granted to copy and distribute modified versions of this | |
11 | .\" manual under the conditions for verbatim copying, provided that the | |
12 | .\" entire resulting derived work is distributed under the terms of a | |
13 | .\" permission notice identical to this one. | |
c13182ef | 14 | .\" |
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15 | .\" Since the Linux kernel and libraries are constantly changing, this |
16 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
17 | .\" responsibility for errors or omissions, or for damages resulting from | |
18 | .\" the use of the information contained herein. The author(s) may not | |
19 | .\" have taken the same level of care in the production of this manual, | |
20 | .\" which is licensed free of charge, as they might when working | |
21 | .\" professionally. | |
c13182ef | 22 | .\" |
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23 | .\" Formatted or processed versions of this manual, if unaccompanied by |
24 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 25 | .\" %%%LICENSE_END |
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26 | .\" |
27 | .\" Inspired by a page by Walter Harms created 2002-08-10 | |
28 | .\" | |
4b8c67d9 | 29 | .TH ILOGB 3 2017-09-15 "" "Linux Programmer's Manual" |
fea681da | 30 | .SH NAME |
d33cd73d | 31 | ilogb, ilogbf, ilogbl \- get integer exponent of a floating-point value |
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32 | .SH SYNOPSIS |
33 | .B #include <math.h> | |
68e4db0a | 34 | .PP |
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35 | .BI "int ilogb(double " x ); |
36 | .br | |
37 | .BI "int ilogbf(float " x ); | |
38 | .br | |
39 | .BI "int ilogbl(long double " x ); | |
68e4db0a | 40 | .PP |
20c58d70 | 41 | Link with \fI\-lm\fP. |
68e4db0a | 42 | .PP |
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43 | .in -4n |
44 | Feature Test Macro Requirements for glibc (see | |
45 | .BR feature_test_macros (7)): | |
46 | .in | |
68e4db0a | 47 | .PP |
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48 | .ad l |
49 | .BR ilogb (): | |
70cb8d5e | 50 | .RS 4 |
cf7fa0a1 | 51 | _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L |
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52 | || _XOPEN_SOURCE\ >=\ 500 |
53 | .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED | |
54 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE | |
55 | || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE | |
70cb8d5e | 56 | .RE |
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57 | .br |
58 | .BR ilogbf (), | |
59 | .BR ilogbl (): | |
70cb8d5e | 60 | .RS 4 |
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61 | _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L |
62 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE | |
63 | || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE | |
70cb8d5e | 64 | .RE |
d33cd73d | 65 | .ad b |
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66 | .SH DESCRIPTION |
67 | These functions return the exponent part of their argument | |
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68 | as a signed integer. |
69 | When no error occurs, these functions | |
fea681da | 70 | are equivalent to the corresponding |
fb186734 | 71 | .BR logb (3) |
7d2cb9d5 | 72 | functions, cast to |
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73 | .IR int . |
74 | .SH RETURN VALUE | |
75 | On success, these functions return the exponent of | |
76 | .IR x , | |
77 | as a signed integer. | |
847e0d88 | 78 | .PP |
fea681da MK |
79 | If |
80 | .I x | |
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81 | is zero, then a domain error occurs, and the functions return |
82 | .\" the POSIX.1 spec for logb() says logb() gives pole error for this | |
83 | .\" case, but for ilogb() it says domain error. | |
d33cd73d | 84 | .BR FP_ILOGB0 . |
fea681da | 85 | .\" glibc: The numeric value is either `INT_MIN' or `-INT_MAX'. |
847e0d88 | 86 | .PP |
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87 | If |
88 | .I x | |
efe294cb | 89 | is a NaN, then a domain error occurs, and the functions return |
d33cd73d | 90 | .BR FP_ILOGBNAN . |
fea681da | 91 | .\" glibc: The numeric value is either `INT_MIN' or `INT_MAX'. |
d33cd73d | 92 | .\" On i386, FP_ILOGB0 and FP_ILOGBNAN have the same value. |
847e0d88 | 93 | .PP |
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94 | If |
95 | .I x | |
d33cd73d | 96 | is negative infinity or positive infinity, then |
efe294cb | 97 | a domain error occurs, and the functions return |
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98 | .BR INT_MAX . |
99 | .\" | |
100 | .\" POSIX.1-2001 also says: | |
4e836144 | 101 | .\" If the correct value is greater than {INT_MAX}, {INT_MAX} |
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102 | .\" shall be returned and a domain error shall occur. |
103 | .\" | |
104 | .\" If the correct value is less than {INT_MIN}, {INT_MIN} | |
4e836144 | 105 | .\" shall be returned and a domain error shall occur. |
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106 | .SH ERRORS |
107 | See | |
108 | .BR math_error (7) | |
109 | for information on how to determine whether an error has occurred | |
110 | when calling these functions. | |
111 | .PP | |
112 | The following errors can occur: | |
113 | .TP | |
114 | Domain error: \fIx\fP is 0 or a NaN | |
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115 | An invalid floating-point exception |
116 | .RB ( FE_INVALID ) | |
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117 | is raised, and |
118 | .I errno | |
119 | is set to | |
120 | .BR EDOM | |
121 | (but see BUGS). | |
d33cd73d | 122 | .IP |
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123 | .TP |
124 | Domain error: \fIx\fP is an infinity | |
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125 | An invalid floating-point exception |
126 | .RB ( FE_INVALID ) | |
127 | is raised, and | |
128 | .I errno | |
129 | is set to | |
130 | .BR EDOM | |
131 | (but see BUGS). | |
ea00bcb3 | 132 | .SH ATTRIBUTES |
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133 | For an explanation of the terms used in this section, see |
134 | .BR attributes (7). | |
135 | .TS | |
136 | allbox; | |
137 | lbw27 lb lb | |
138 | l l l. | |
139 | Interface Attribute Value | |
140 | T{ | |
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141 | .BR ilogb (), |
142 | .BR ilogbf (), | |
ea00bcb3 | 143 | .BR ilogbl () |
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144 | T} Thread safety MT-Safe |
145 | .TE | |
47297adb | 146 | .SH CONFORMING TO |
9a74e018 | 147 | C99, POSIX.1-2001, POSIX.1-2008. |
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148 | .SH BUGS |
149 | .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6794 | |
b5fafa0b | 150 | Before version 2.16, the following bugs existed in the |
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151 | glibc implementation of these functions: |
152 | .IP * 3 | |
153 | The domain error case where | |
154 | .I x | |
155 | is 0 or a NaN did not cause | |
156 | .I errno | |
18e93ab8 | 157 | to be set or (on some architectures) raise a floating-point exception. |
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158 | .IP * 3 |
159 | The domain error case where | |
160 | .I x | |
161 | is an infinity did not cause | |
162 | .I errno | |
163 | to be set or raise a floating-point exception. | |
47297adb | 164 | .SH SEE ALSO |
fea681da | 165 | .BR log (3), |
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166 | .BR logb (3), |
167 | .BR significand (3) |