# gamma1pm1
> Compute `gamma(x+1) - 1`.
## Usage
```javascript
var gamma1pm1 = require( '@stdlib/math/base/special/gamma1pm1' );
```
#### gamma1pm1( x )
Computes `gamma(x+1) - 1` without cancellation errors for small `x` and where `gamma(x)` is the [gamma function][@stdlib/math/base/special/gamma].
```javascript
var v = gamma1pm1( 0.2 );
// returns ~-0.082
v = gamma1pm1( -8.5 );
// returns ~-1.0
v = gamma1pm1( 0.0 );
// returns 0.0
v = gamma1pm1( NaN );
// returns NaN
```
## Examples
```javascript
var randu = require( '@stdlib/random/base/randu' );
var gamma1pm1 = require( '@stdlib/math/base/special/gamma1pm1' );
var x;
var i;
for ( i = 0; i < 100; i++ ) {
x = (randu()*10.0) - 5.0;
console.log( 'gamma(%d+1) - 1 = %d', x, gamma1pm1( x ) );
}
```
[@stdlib/math/base/special/gamma]: https://www.npmjs.com/package/@stdlib/math/tree/main/base/special/gamma