time-to-botec/squiggle/node_modules/@stdlib/math/base/special/inv/README.md

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# inv

> Compute the [multiplicative inverse][multiplicative-inverse] of a double-precision floating-point number.

<section class="intro">

The [multiplicative inverse][multiplicative-inverse] (or **reciprocal**) is defined as

<!-- <equation class="equation" label="eq:multiplicative_inverse" align="center" raw="y = \frac{1}{x}" alt="Multiplicative inverse"> -->

<div class="equation" align="center" data-raw-text="y = \frac{1}{x}" data-equation="eq:multiplicative_inverse">
    <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@bb29798906e119fcb2af99e94b60407a270c9b32/lib/node_modules/@stdlib/math/base/special/inv/docs/img/equation_multiplicative_inverse.svg" alt="Multiplicative inverse">
    <br>
</div>

<!-- </equation> -->

</section>

<!-- /.intro -->

<section class="usage">

## 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
```

</section>

<!-- /.usage -->

<section class="examples">

## Examples

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

```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 ) );
}
```

</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/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 );
```

</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/inv.h"
#include <stdio.h>

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 );
    }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<section class="links">

[multiplicative-inverse]: https://en.wikipedia.org/wiki/Multiplicative_inverse

</section>

<!-- /.links -->