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2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
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27 .\" Inspired by a page by Walter Harms created 2002-08-10
29 .TH ILOGB 3 2013-08-06 "" "Linux Programmer's Manual"
31 ilogb, ilogbf, ilogbl \- get integer exponent of a floating-point value
35 .BI "int ilogb(double " x );
37 .BI "int ilogbf(float " x );
39 .BI "int ilogbl(long double " x );
44 Feature Test Macro Requirements for glibc (see
45 .BR feature_test_macros (7)):
51 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
52 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED ||
54 _POSIX_C_SOURCE\ >=\ 200112L;
63 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
64 _POSIX_C_SOURCE\ >=\ 200112L;
71 These functions return the exponent part of their argument
73 When no error occurs, these functions
74 are equivalent to the corresponding
79 On success, these functions return the exponent of
85 is zero, then a domain error occurs, and the functions return
86 .\" the POSIX.1 spec for logb() says logb() gives pole error for this
87 .\" case, but for ilogb() it says domain error.
89 .\" glibc: The numeric value is either `INT_MIN' or `-INT_MAX'.
93 is a NaN, then a domain error occurs, and the functions return
95 .\" glibc: The numeric value is either `INT_MIN' or `INT_MAX'.
96 .\" On i386, FP_ILOGB0 and FP_ILOGBNAN have the same value.
100 is negative infinity or positive infinity, then
101 a domain error occurs, and the functions return
104 .\" POSIX.1-2001 also says:
105 .\" If the correct value is greater than {INT_MAX}, {INT_MAX}
106 .\" shall be returned and a domain error shall occur.
108 .\" If the correct value is less than {INT_MIN}, {INT_MIN}
109 .\" shall be returned and a domain error shall occur.
113 for information on how to determine whether an error has occurred
114 when calling these functions.
116 The following errors can occur:
118 Domain error: \fIx\fP is 0 or a NaN
122 An invalid floating-point exception
126 These functions do not set
129 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6794
131 Domain error: \fIx\fP is an infinity
135 .\" An invalid floating-point exception
136 .\" .RB ( FE_INVALID )
139 These functions do not set
141 or raise an exception for this case.
142 .\" FIXME . Is it intentional that these functions do not set errno,
143 .\" or raise an exception?
144 .\" log(), log2(), log10() do set errno
145 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6794
147 .SS Multithreading (see pthreads(7))
153 functions are thread-safe.