1 .\" Copyright 1995 Jim Van Zandt <jrv@vanzandt.mv.com>
2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
3 .\" <mtk.manpages@gmail.com>
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27 .\" Modified 2002-07-27 Walter Harms
28 .\" (walter.harms@informatik.uni-oldenburg.de)
30 .TH EXPM1 3 2013-10-14 "" "Linux Programmer's Manual"
32 expm1, expm1f, expm1l \- exponential minus 1
37 .BI "double expm1(double " x );
39 .BI "float expm1f(float " x );
41 .BI "long double expm1l(long double " x );
47 Feature Test Macro Requirements for glibc (see
48 .BR feature_test_macros (7)):
54 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
55 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE ||
56 _POSIX_C_SOURCE\ >=\ 200112L;
65 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
66 _POSIX_C_SOURCE\ >=\ 200112L;
74 returns a value equivalent to
81 computed in a way that is accurate even if the value of
86 would be inaccurate due to
87 subtraction of two numbers that are nearly equal.
89 On success, these functions return
100 +0 (\-0) is returned.
104 is positive infinity, positive infinity is returned.
108 is negative infinity, \-1 is returned.
110 If the result overflows, a range error occurs,
111 and the functions return
120 for information on how to determine whether an error has occurred
121 when calling these functions.
123 The following errors can occur:
125 Range error, overflow
130 An overflow floating-point exception
134 .\" POSIX.1 specifies an optional range error (underflow) if
135 .\" x is subnormal. Glibc does not implement this.
137 .SS Multithreading (see pthreads(7))
143 functions are thread-safe.
148 For some large negative
150 values (where the function result approaches \-1),
152 raises a bogus underflow floating-point exception.
154 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6778
156 For some large positive
160 raises a bogus invalid floating-point exception in addition to the expected
161 overflow exception, and returns a NaN instead of positive infinity.
163 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6814
164 .\" e.g., expm1(1e5) through expm1(1.00199970127e5),
165 .\" but not expm1(1.00199970128e5) and beyond.
168 .\" It looks like the fix was in 2.11, or possibly 2.12.
169 .\" I have no test system for 2.11, but 2.12 passes.
170 .\" From the source (sysdeps/i386/fpu/s_expm1.S) it looks
171 .\" like the changes were in 2.11.
172 the glibc implementation did not set
173 .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6788
177 when a range error occurred.
183 This page is part of release 3.79 of the Linux
186 A description of the project,
187 information about reporting bugs,
188 and the latest version of this page,
190 \%http://www.kernel.org/doc/man\-pages/.