man pages section 3: Extended Library Functions, Volume 2
Updated: July 2014

## exp(3M)

### Name

exp, expf, expl - exponential function

### Synopsis

```c99 [ flag... ] file... –lm [ library... ]
#include <math.h>

double exp(double x);```
`float expf(float x);`
`long double expl(long double x);`

### Description

These functions compute the base-e exponential of x.

### Return Values

Upon successful completion, these functions return the exponential value of x.

If the correct value would cause overflow, a range error occurs and exp(), expf(), and expl() return HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.

If x is NaN, a NaN is returned.

If x is ±0, 1 is returned.

If x is +Inf, x is returned.

For exceptional cases, matherr(3M) tabulates the values to be returned by exp() as specified by SVID3 and XPG3. See standards(5).

### Errors

These functions will fail if:

Range Error

The result overflows.

If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the overflow floating-point exception is raised.

The exp() function sets errno to ERANGE if the result overflows.

### Usage

An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions.

An application can also set errno to 0 before calling exp(). On return, if errno is non-zero, an error has occurred. The expf() and expl() functions do not set errno.

### Attributes

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
MT-Level
MT-Safe
Standard