.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
+.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
+.\" <mtk.manpages@gmail.com>
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.\" entire resulting derived work is distributed under the terms of a
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.\" have taken the same level of care in the production of this manual,
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.\" References consulted:
.\" Linux libc source code
.\" Modified 2002-07-27 by Walter Harms
.\" (walter.harms@informatik.uni-oldenburg.de)
.\"
-.TH EXP 3 2002-07-27 "" "Linux Programmer's Manual"
+.TH EXP 3 2017-09-15 "" "Linux Programmer's Manual"
.SH NAME
exp, expf, expl \- base-e exponential function
.SH SYNOPSIS
.nf
.B #include <math.h>
-.sp
+.PP
.BI "double exp(double " x );
-.br
.BI "float expf(float " x );
-.br
.BI "long double expl(long double " x );
.fi
-.sp
-Link with \-lm.
+.PP
+Link with \fI\-lm\fP.
+.PP
+.in -4n
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.in
+.PP
+.ad l
+.BR expf (),
+.BR expl ():
+.RS 4
+_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
-The \fBexp()\fP function returns the value of e (the base of natural
-logarithms) raised to the power of \fIx\fP.
-.SH "CONFORMING TO"
-SVID 3, POSIX, BSD 4.3, ISO 9899.
-The float and the long double variants are C99 requirements.
-.SH "SEE ALSO"
+These functions return the value of e (the base of natural
+logarithms) raised to the power of
+.IR x .
+.SH RETURN VALUE
+On success, these functions return the exponential value of
+.IR x .
+.PP
+If
+.I x
+is a NaN,
+a NaN is returned.
+.PP
+If
+.I x
+is positive infinity,
+positive infinity is returned.
+.PP
+If
+.I x
+is negative infinity,
++0 is returned.
+.PP
+If the result underflows,
+a range error occurs,
+and zero is returned.
+.PP
+If the result overflows,
+a range error occurs,
+and the functions return
+.RB + HUGE_VAL ,
+.RB + HUGE_VALF ,
+or
+.RB + HUGE_VALL ,
+respectively.
+.SH ERRORS
+See
+.BR math_error (7)
+for information on how to determine whether an error has occurred
+when calling these functions.
+.PP
+The following errors can occur:
+.TP
+Range error, overflow
+.I errno
+is set to
+.BR ERANGE .
+An overflow floating-point exception
+.RB ( FE_OVERFLOW )
+is raised.
+.TP
+Range error, underflow
+.I errno
+is set to
+.BR ERANGE .
+An underflow floating-point exception
+.RB ( FE_UNDERFLOW )
+is raised.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbw21 lb lb
+l l l.
+Interface Attribute Value
+T{
+.BR exp (),
+.BR expf (),
+.BR expl ()
+T} Thread safety MT-Safe
+.TE
+.SH CONFORMING TO
+C99, POSIX.1-2001, POSIX.1-2008.
+.PP
+The variant returning
+.I double
+also conforms to
+SVr4, 4.3BSD, C89.
+.SH SEE ALSO
.BR cbrt (3),
+.BR cexp (3),
.BR exp10 (3),
.BR exp2 (3),
+.BR expm1 (3),
.BR sqrt (3)
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