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.\" Copyright 1995 Jim Van Zandt <jrv@vanzandt.mv.com>
.\"
.\" 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.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date. The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein. The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.\" Modified 2002-07-27 Walter Harms
.\" (walter.harms@informatik.uni-oldenburg.de)
.\"
.TH EXPM1 3 2007-07-26 "" "Linux Programmer's Manual"
.SH NAME
expm1, expm1f, expm1l \- exponential minus 1
.SH SYNOPSIS
.nf
.B #include <math.h>
.sp
.BI "double expm1(double " x );
.br
.BI "float expm1f(float " x );
.br
.BI "long double expm1l(long double " x );
.sp
.fi
Link with \fI-lm\fP.
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.ad l
.BR expm1 (),
.BR expm1f (),
.BR expm1l ():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 || _ISOC99_SOURCE; or
.I cc\ -std=c99
.ad b
.SH DESCRIPTION
.BI expm1( x )
returns a value equivalent to `exp (\fIx\fP) \- 1'.
It is
computed in a way that is accurate even if the value of \fIx\fP is near
zero\(ema case where `exp (\fIx\fP) \- 1' would be inaccurate due to
subtraction of two numbers that are nearly equal.
.SH "CONFORMING TO"
BSD, C99.
The
.I float
and
.I "long double"
variants are C99 requirements.
.SH "SEE ALSO"
.BR exp (3),
.BR log (3),
.BR log1p (3)
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