exp(3) Library Functions Manual exp(3)

# NAME

exp, expf, expl - base-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:

errno is set to ERANGE. An overflow floating-point exception (FE_OVERFLOW) is raised.
errno is set to ERANGE. An underflow floating-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 MT-Safe

# STANDARDS

C99, POSIX.1-2001, POSIX.1-2008.

The variant returning double also conforms to SVr4, 4.3BSD, C89.