]>
Commit | Line | Data |
---|---|---|
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 | .\" |
5fbde956 | 5 | .\" SPDX-License-Identifier: Linux-man-pages-copyleft |
fea681da MK |
6 | .\" |
7 | .\" Inspired by a page by Walter Harms created 2002-08-10 | |
8 | .\" | |
1d767b55 | 9 | .TH ILOGB 3 2021-03-22 "" "Linux Programmer's Manual" |
fea681da | 10 | .SH NAME |
d33cd73d | 11 | ilogb, ilogbf, ilogbl \- get integer exponent of a floating-point value |
2af19291 AC |
12 | .SH LIBRARY |
13 | Math library | |
8fc3b2cf | 14 | .RI ( libm ", " \-lm ) |
fea681da | 15 | .SH SYNOPSIS |
c7db92b9 | 16 | .nf |
fea681da | 17 | .B #include <math.h> |
68e4db0a | 18 | .PP |
fea681da | 19 | .BI "int ilogb(double " x ); |
fea681da | 20 | .BI "int ilogbf(float " x ); |
fea681da | 21 | .BI "int ilogbl(long double " x ); |
c7db92b9 | 22 | .fi |
68e4db0a | 23 | .PP |
d39ad78f | 24 | .RS -4 |
d33cd73d MK |
25 | Feature Test Macro Requirements for glibc (see |
26 | .BR feature_test_macros (7)): | |
d39ad78f | 27 | .RE |
68e4db0a | 28 | .PP |
d33cd73d | 29 | .BR ilogb (): |
9d2adbae | 30 | .nf |
5c10d2c5 MK |
31 | _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L |
32 | || _XOPEN_SOURCE >= 500 | |
33 | .\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED | |
9d2adbae MK |
34 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE |
35 | || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE | |
36 | .fi | |
0129eef2 | 37 | .PP |
d33cd73d MK |
38 | .BR ilogbf (), |
39 | .BR ilogbl (): | |
9d2adbae | 40 | .nf |
5c10d2c5 | 41 | _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L |
9d2adbae MK |
42 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE |
43 | || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE | |
44 | .fi | |
fea681da MK |
45 | .SH DESCRIPTION |
46 | These functions return the exponent part of their argument | |
c13182ef MK |
47 | as a signed integer. |
48 | When no error occurs, these functions | |
fea681da | 49 | are equivalent to the corresponding |
fb186734 | 50 | .BR logb (3) |
7d2cb9d5 | 51 | functions, cast to |
d33cd73d MK |
52 | .IR int . |
53 | .SH RETURN VALUE | |
54 | On success, these functions return the exponent of | |
55 | .IR x , | |
56 | as a signed integer. | |
847e0d88 | 57 | .PP |
fea681da MK |
58 | If |
59 | .I x | |
efe294cb MK |
60 | is zero, then a domain error occurs, and the functions return |
61 | .\" the POSIX.1 spec for logb() says logb() gives pole error for this | |
62 | .\" case, but for ilogb() it says domain error. | |
d33cd73d | 63 | .BR FP_ILOGB0 . |
fea681da | 64 | .\" glibc: The numeric value is either `INT_MIN' or `-INT_MAX'. |
847e0d88 | 65 | .PP |
fea681da MK |
66 | If |
67 | .I x | |
efe294cb | 68 | is a NaN, then a domain error occurs, and the functions return |
d33cd73d | 69 | .BR FP_ILOGBNAN . |
fea681da | 70 | .\" glibc: The numeric value is either `INT_MIN' or `INT_MAX'. |
d33cd73d | 71 | .\" On i386, FP_ILOGB0 and FP_ILOGBNAN have the same value. |
847e0d88 | 72 | .PP |
fea681da MK |
73 | If |
74 | .I x | |
d33cd73d | 75 | is negative infinity or positive infinity, then |
efe294cb | 76 | a domain error occurs, and the functions return |
d33cd73d MK |
77 | .BR INT_MAX . |
78 | .\" | |
79 | .\" POSIX.1-2001 also says: | |
4e836144 | 80 | .\" If the correct value is greater than {INT_MAX}, {INT_MAX} |
d33cd73d MK |
81 | .\" shall be returned and a domain error shall occur. |
82 | .\" | |
83 | .\" If the correct value is less than {INT_MIN}, {INT_MIN} | |
4e836144 | 84 | .\" shall be returned and a domain error shall occur. |
d33cd73d MK |
85 | .SH ERRORS |
86 | See | |
87 | .BR math_error (7) | |
88 | for information on how to determine whether an error has occurred | |
89 | when calling these functions. | |
90 | .PP | |
91 | The following errors can occur: | |
92 | .TP | |
93 | Domain error: \fIx\fP is 0 or a NaN | |
d33cd73d MK |
94 | An invalid floating-point exception |
95 | .RB ( FE_INVALID ) | |
8ee4373d MK |
96 | is raised, and |
97 | .I errno | |
98 | is set to | |
99 | .BR EDOM | |
100 | (but see BUGS). | |
d33cd73d MK |
101 | .TP |
102 | Domain error: \fIx\fP is an infinity | |
8ee4373d MK |
103 | An invalid floating-point exception |
104 | .RB ( FE_INVALID ) | |
105 | is raised, and | |
106 | .I errno | |
107 | is set to | |
108 | .BR EDOM | |
109 | (but see BUGS). | |
ea00bcb3 | 110 | .SH ATTRIBUTES |
5b0d5aef MK |
111 | For an explanation of the terms used in this section, see |
112 | .BR attributes (7). | |
c466875e MK |
113 | .ad l |
114 | .nh | |
5b0d5aef MK |
115 | .TS |
116 | allbox; | |
c466875e | 117 | lbx lb lb |
5b0d5aef MK |
118 | l l l. |
119 | Interface Attribute Value | |
120 | T{ | |
ea00bcb3 PH |
121 | .BR ilogb (), |
122 | .BR ilogbf (), | |
ea00bcb3 | 123 | .BR ilogbl () |
5b0d5aef MK |
124 | T} Thread safety MT-Safe |
125 | .TE | |
c466875e MK |
126 | .hy |
127 | .ad | |
128 | .sp 1 | |
47297adb | 129 | .SH CONFORMING TO |
9a74e018 | 130 | C99, POSIX.1-2001, POSIX.1-2008. |
8ee4373d MK |
131 | .SH BUGS |
132 | .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6794 | |
b5fafa0b | 133 | Before version 2.16, the following bugs existed in the |
8ee4373d MK |
134 | glibc implementation of these functions: |
135 | .IP * 3 | |
136 | The domain error case where | |
137 | .I x | |
138 | is 0 or a NaN did not cause | |
139 | .I errno | |
18e93ab8 | 140 | to be set or (on some architectures) raise a floating-point exception. |
8ee4373d MK |
141 | .IP * 3 |
142 | The domain error case where | |
143 | .I x | |
144 | is an infinity did not cause | |
145 | .I errno | |
146 | to be set or raise a floating-point exception. | |
47297adb | 147 | .SH SEE ALSO |
fea681da | 148 | .BR log (3), |
55975b54 MK |
149 | .BR logb (3), |
150 | .BR significand (3) |