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 2017-09-15 "" "Linux Programmer's Manual"
32 expm1, expm1f, expm1l \- exponential minus 1
37 .BI "double expm1(double " x );
38 .BI "float expm1f(float " x );
39 .BI "long double expm1l(long double " x );
45 Feature Test Macro Requirements for glibc (see
46 .BR feature_test_macros (7)):
52 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
53 || _XOPEN_SOURCE\ >=\ 500
54 .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
55 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
56 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
62 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
63 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
64 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
68 These functions return a value equivalent to
74 The result is computed in a way that is accurate even if the value of
79 would be inaccurate due to
80 subtraction of two numbers that are nearly equal.
82 On success, these functions return
97 is positive infinity, positive infinity is returned.
101 is negative infinity, \-1 is returned.
103 If the result overflows, a range error occurs,
104 and the functions return
113 for information on how to determine whether an error has occurred
114 when calling these functions.
116 The following errors can occur:
118 Range error, overflow
123 An overflow floating-point exception
127 .\" POSIX.1 specifies an optional range error (underflow) if
128 .\" x is subnormal. Glibc does not implement this.
130 For an explanation of the terms used in this section, see
136 Interface Attribute Value
141 T} Thread safety MT-Safe
144 C99, POSIX.1-2001, POSIX.1-2008.
147 For some large negative
149 values (where the function result approaches \-1),
151 raises a bogus underflow floating-point exception.
153 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6778
155 For some large positive
159 raises a bogus invalid floating-point exception in addition to the expected
160 overflow exception, and returns a NaN instead of positive infinity.
162 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6814
163 .\" e.g., expm1(1e5) through expm1(1.00199970127e5),
164 .\" but not expm1(1.00199970128e5) and beyond.
167 .\" It looks like the fix was in 2.11, or possibly 2.12.
168 .\" I have no test system for 2.11, but 2.12 passes.
169 .\" From the source (sysdeps/i386/fpu/s_expm1.S) it looks
170 .\" like the changes were in 2.11.
171 the glibc implementation did not set
172 .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6788
176 when a range error occurred.