# Natural Exponential Function
> Natural [exponential function][exponential-function].
The natural [exponential function][exponential-function] is defined as
where `e` is [Euler's][@stdlib/constants/float64/e] number.
## Usage
```javascript
var exp = require( '@stdlib/math/base/special/exp' );
```
#### exp( x )
Evaluates the natural [exponential function][exponential-function].
```javascript
var v = exp( 4.0 );
// returns ~54.5982
v = exp( -9.0 );
// returns ~1.234e-4
v = exp( 0.0 );
// returns 1.0
v = exp( NaN );
// returns NaN
```
## Examples
```javascript
var randu = require( '@stdlib/random/base/randu' );
var exp = require( '@stdlib/math/base/special/exp' );
var x;
var i;
for ( i = 0; i < 100; i++ ) {
x = (randu()*100.0) - 50.0;
console.log( 'e^%d = %d', x, exp( x ) );
}
```
[exponential-function]: https://en.wikipedia.org/wiki/Exponential_function
[@stdlib/constants/float64/e]: https://www.npmjs.com/package/@stdlib/constants-float64-e
