1 .\" Copyright 1995 Jim Van Zandt <jrv@vanzandt.mv.com>
2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
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27 .\" Modified 2002-07-27 Walter Harms
28 .\" (walter.harms@informatik.uni-oldenburg.de)
30 .TH EXPM1 3 2016-03-15 "" "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 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
55 || _XOPEN_SOURCE\ >=\ 500
56 .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
57 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
58 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
64 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
65 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
66 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
70 These functions return a value equivalent to
76 The result is computed in a way that is accurate even if the value of
81 would be inaccurate due to
82 subtraction of two numbers that are nearly equal.
84 On success, these functions return
99 is positive infinity, positive infinity is returned.
103 is negative infinity, \-1 is returned.
105 If the result overflows, a range error occurs,
106 and the functions return
115 for information on how to determine whether an error has occurred
116 when calling these functions.
118 The following errors can occur:
120 Range error, overflow
125 An overflow floating-point exception
129 .\" POSIX.1 specifies an optional range error (underflow) if
130 .\" x is subnormal. Glibc does not implement this.
132 For an explanation of the terms used in this section, see
138 Interface Attribute Value
143 T} Thread safety MT-Safe
146 C99, POSIX.1-2001, POSIX.1-2008.
149 For some large negative
151 values (where the function result approaches \-1),
153 raises a bogus underflow floating-point exception.
155 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6778
157 For some large positive
161 raises a bogus invalid floating-point exception in addition to the expected
162 overflow exception, and returns a NaN instead of positive infinity.
164 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6814
165 .\" e.g., expm1(1e5) through expm1(1.00199970127e5),
166 .\" but not expm1(1.00199970128e5) and beyond.
169 .\" It looks like the fix was in 2.11, or possibly 2.12.
170 .\" I have no test system for 2.11, but 2.12 passes.
171 .\" From the source (sysdeps/i386/fpu/s_expm1.S) it looks
172 .\" like the changes were in 2.11.
173 the glibc implementation did not set
174 .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6788
178 when a range error occurred.