# inv
> Compute the [multiplicative inverse][multiplicative-inverse] of a double-precision floating-point number.
The [multiplicative inverse][multiplicative-inverse] (or **reciprocal**) is defined as
## Usage
```javascript
var inv = require( '@stdlib/math/base/special/inv' );
```
#### inv( x )
Computes the [multiplicative inverse][multiplicative-inverse] of a double-precision floating-point number `x`.
```javascript
var v = inv( -1.0 );
// returns -1.0
v = inv( 2.0 );
// returns 0.5
v = inv( 0.0 );
// returns Infinity
v = inv( -0.0 );
// returns -Infinity
v = inv( NaN );
// returns NaN
```
## Examples
```javascript
var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var inv = require( '@stdlib/math/base/special/inv' );
var x;
var i;
for ( i = 0; i < 100; i++ ) {
x = round( randu()*100.0 ) - 50.0;
console.log( 'inv(%d) = %d', x, inv( x ) );
}
```
* * *
## C APIs
### Usage
```c
#include "stdlib/math/base/special/inv.h"
```
#### stdlib_base_inv( x )
Computes the multiplicative inverse of a double-precision floating-point number.
```c
double y = stdlib_base_inv( 2.0 );
// returns 0.5
```
The function accepts the following arguments:
- **x**: `[in] double` input value.
```c
double stdlib_base_inv( const double x );
```
### Examples
```c
#include "stdlib/math/base/special/inv.h"
#include
int main() {
double x[] = { 3.0, 4.0, 5.0, 12.0 };
double y;
int i;
for ( i = 0; i < 4; i++ ) {
y = stdlib_base_inv( x[ i ] );
printf( "inv(%lf) = %lf\n", x[ i ], y );
}
}
```
[multiplicative-inverse]: https://en.wikipedia.org/wiki/Multiplicative_inverse
