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'\" t
.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH exp 3 2025-05-17 "Linux man-pages (unreleased)"
.SH NAME
exp, expf, expl \- base-e exponential function
.SH LIBRARY
Math library
.RI ( libm ,\~ \-lm )
.SH SYNOPSIS
.nf
.B #include <math.h>
.P
.BI "double exp(double " x );
.BI "float expf(float " x );
.BI "long double expl(long double " x );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.BR expf (),
.BR expl ():
.nf
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.fi
.SH DESCRIPTION
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 .
.P
If
.I x
is a NaN,
a NaN is returned.
.P
If
.I x
is positive infinity,
positive infinity is returned.
.P
If
.I x
is negative infinity,
+0 is returned.
.P
If the result underflows,
a range error occurs,
and zero is returned.
.P
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.
.P
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;
lbx lb lb
l l l.
Interface Attribute Value
T{
.na
.nh
.BR exp (),
.BR expf (),
.BR expl ()
T} Thread safety MT-Safe
.TE
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
C99, POSIX.1-2001.
.P
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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