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exp

Section: C Library Functions (3)
Updated: 202-0-08
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NAME

exp, expf, expl - bas-e exponential function

LIBRARY

Math library (libm,~-lm)

SYNOPSIS

#include <math.h>
double exp(double x);
float expf(float x);
long double expl(long double x);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)): expf(), expl():

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

These functions return the value of e (the base of natural logarithms) raised to the power of x.

RETURN VALUE

On success, these functions return the exponential value of x. If x is a NaN, a NaN is returned. If x is positive infinity, positive infinity is returned. If x is negative infinity, +0 is returned. If the result underflows, a range error occurs, and zero is returned. If the result overflows, a range error occurs, and the functions return +HUGE_VAL, +HUGE_VALF, or +HUGE_VALL, respectively.

ERRORS

See math_error(7) for information on how to determine whether an error has occurred when calling these functions. The following errors can occur:

Range error, overflow: errno is set to ERANGE. An overflow floatin-point exception (FE_OVERFLOW) is raised.
Range error, underflow: errno is set to ERANGE. An underflow floatin-point exception (FE_UNDERFLOW) is raised.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
exp(), expf(), expl()	Thread safety	M-Safe

STANDARDS

C11, POSIX.-2008.

HISTORY

C99, POSIX.-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.