.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
.\" <mtk.manpages@gmail.com>
.\"
+.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
+.\" %%%LICENSE_END
.\"
.\" Modified 2002-07-27 Walter Harms
.\" (walter.harms@informatik.uni-oldenburg.de)
.\"
-.TH EXPM1 3 2010-09-12 "" "Linux Programmer's Manual"
+.TH EXPM1 3 2017-09-15 "" "Linux Programmer's Manual"
.SH NAME
expm1, expm1f, expm1l \- exponential minus 1
.SH SYNOPSIS
.nf
.B #include <math.h>
-.sp
+.PP
.BI "double expm1(double " x );
-.br
.BI "float expm1f(float " x );
-.br
.BI "long double expm1l(long double " x );
-.sp
+.PP
.fi
Link with \fI\-lm\fP.
-.sp
+.PP
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
-.sp
+.PP
.ad l
.BR expm1 ():
.RS 4
-_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
-_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE ||
-_POSIX_C_SOURCE >= 200112L;
-.br
-or
-.I cc\ -std=c99
+_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
+ || _XOPEN_SOURCE\ >=\ 500
+.\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
+ || /* Since glibc 2.19: */ _DEFAULT_SOURCE
+ || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.RE
.br
.BR expm1f (),
.BR expm1l ():
.RS 4
-_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
-_POSIX_C_SOURCE >= 200112L;
-.br
-or
-.I cc\ -std=c99
+_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
+ || /* Since glibc 2.19: */ _DEFAULT_SOURCE
+ || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.RE
.ad b
.SH DESCRIPTION
-.I expm1(x)
-returns a value equivalent to
+These functions return a value equivalent to
+.PP
.nf
-
exp(x) \- 1
-
.fi
-It is
-computed in a way that is accurate even if the value of \fIx\fP is near
+.PP
+The result is computed in a way that is accurate even if the value of
+.I x
+is near
zero\(ema case where
.I "exp(x) \- 1"
would be inaccurate due to
.SH RETURN VALUE
On success, these functions return
.IR "exp(x)\ \-\ 1" .
-
+.PP
If
.I x
is a NaN,
a NaN is returned.
-
+.PP
If
.I x
is +0 (\-0),
+0 (\-0) is returned.
-
+.PP
If
.I x
is positive infinity, positive infinity is returned.
-
+.PP
If
.I x
is negative infinity, \-1 is returned.
-
+.PP
If the result overflows, a range error occurs,
and the functions return
.RB - HUGE_VAL ,
.\"
.\" POSIX.1 specifies an optional range error (underflow) if
.\" x is subnormal. Glibc does not implement this.
-.SH "CONFORMING TO"
-C99, POSIX.1-2001.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbw27 lb lb
+l l l.
+Interface Attribute Value
+T{
+.BR expm1 (),
+.BR expm1f (),
+.BR expm1l ()
+T} Thread safety MT-Safe
+.TE
+.SH CONFORMING TO
+C99, POSIX.1-2001, POSIX.1-2008.
.\" BSD.
.SH BUGS
-For some large negative
+Before glibc 2.17,
+.\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6778
+on certain architectures (e.g., x86, but not x86_64)
+.BR expm1 ()
+raised a bogus underflow floating-point exception
+for some large negative
.I x
values (where the function result approaches \-1),
+.PP
+Before approximately glibc version 2.11,
+.\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6814
+.\" e.g., expm1(1e5) through expm1(1.00199970127e5),
+.\" but not expm1(1.00199970128e5) and beyond.
.BR expm1 ()
-raises a bogus underflow floating-point exception.
-.\" FIXME .
-.\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6778
-
-For some large positive
+raised a bogus invalid floating-point exception in addition to the expected
+overflow exception, and returned a NaN instead of positive infinity.
+for some large positive
.I x
values,
-.BR expm1 ()
-raises a bogus invalid floating-point exception in addition to the expected
-overflow exception, and returns a NaN instead of positive infinity.
-.\" FIXME .
-.\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6814
-.\" e.g., expm1(1e5) through expm1(1.00199970127e5),
-.\" but not expm1(1.00199970128e5) and beyond.
-
+.PP
Before version 2.11,
.\" It looks like the fix was in 2.11, or possibly 2.12.
.\" I have no test system for 2.11, but 2.12 passes.
to
.B ERANGE
when a range error occurred.
-.SH "SEE ALSO"
+.SH SEE ALSO
.BR exp (3),
.BR log (3),
.BR log1p (3)
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