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# expm1

> Compute `exp(x) - 1`.

<section class="usage">

## Usage

```javascript
var expm1 = require( '@stdlib/math/base/special/expm1' );
```

#### expm1( x )

Computes `exp(x) - 1`, where `exp(x)` is the natural [exponential function][exponential-function].

```javascript
var v = expm1( 0.2 );
// returns ~0.221

v = expm1( -9.0 );
// returns ~-1.0

v = expm1( 0.0 );
// returns 0.0

v = expm1( NaN );
// returns NaN
```

</section>

<!-- /.usage -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var randu = require( '@stdlib/random/base/randu' );
var expm1 = require( '@stdlib/math/base/special/expm1' );

var x;
var i;

for ( i = 0; i < 100; i++ ) {
    x = (randu()*10.0) - 5.0;
    console.log( 'e^%d - 1 = %d', x, expm1( x ) );
}
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/math/base/special/expm1.h"
```

#### stdlib_base_expm1( x )

Computes `exp(x) - 1`, where `exp(x)` is the natural [exponential function][exponential-function].

```c
double out = stdlib_base_expm1( 0.2 );
// returns ~0.221

out = stdlib_base_expm1( -9.0 );
// returns ~-1.0
```

The function accepts the following arguments:

-   **x**: `[in] double` input value.

```c
double stdlib_base_expm1( const double x );
```

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
#include "stdlib/math/base/special/expm1.h"
#include <stdlib.h>
#include <stdio.h>

int main( void ) {
    double x;
    double v;
    int i;
    
    for ( i = 0; i < 100; i++ ) {
        x = ( ( (double)rand() / (double)RAND_MAX ) * 10.0 ) - 5.0;
        v = stdlib_base_expm1( x );
        printf( "e^%lf - 1 = %lf\n", x, v );
    }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/math/base/special/exp`][@stdlib/math/base/special/exp]</span><span class="delimiter">: </span><span class="description">natural exponential function.</span>
-   <span class="package-name">[`@stdlib/math/base/special/expm1rel`][@stdlib/math/base/special/expm1rel]</span><span class="delimiter">: </span><span class="description">relative error exponential.</span>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="links">

[exponential-function]: https://en.wikipedia.org/wiki/Exponential_function

<!-- <related-links> -->

[@stdlib/math/base/special/exp]: https://github.com/stdlib-js/math/tree/main/base/special/exp

[@stdlib/math/base/special/expm1rel]: https://github.com/stdlib-js/math/tree/main/base/special/expm1rel

<!-- </related-links> -->

</section>

<!-- /.links -->
