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# modf

> Decompose a [double-precision floating-point number][ieee754] into integral and fractional parts.

<section class="usage">

## Usage

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

#### modf( \[out,] x )

Decomposes a [double-precision floating-point number][ieee754] into integral and fractional parts, each having the same type and sign as `x`.

```javascript
var parts = modf( 3.14 );
// returns [ 3.0, 0.14000000000000012 ]

parts = modf( +0.0 );
// returns [ +0.0, +0.0 ]

parts = modf( -0.0 );
// returns [ -0.0, -0.0 ]

parts = modf( Infinity );
// returns [ Infinity, +0.0 ]

parts = modf( -Infinity );
// returns [ -Infinity, -0.0 ]

parts = modf( NaN );
// returns [ NaN, NaN ]
```

To avoid unnecessary memory allocation, the function supports providing an output (destination) object.

```javascript
var Float64Array = require( '@stdlib/array/float64' );

var out = new Float64Array( 2 );

var parts = modf( out, 3.14 );
// returns <Float64Array>[ 3.0, 0.14000000000000012 ]

var bool = ( parts === out );
// returns true
```

</section>

<!-- /.usage -->

<section class="notes">

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

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

var parts;
var x;
var i;

for ( i = 0; i < 100; i++ ) {
    x = (randu()*1000.0) - 500.0;
    parts = modf( x );
    console.log( 'modf(%d) => integral: %d. fraction: %d.', x, parts[ 0 ], parts[ 1 ] );
}
```

</section>

<!-- /.examples -->

<section class="links">

[ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985

</section>

<!-- /.links -->