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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( 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 ]
```

#### modf.assign( x, out, stride, offset )

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

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

var out = new Float64Array( 2 );

var parts = modf.assign( 3.14, out, 1, 0 );
// 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 -->

<!-- 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/modf.h"
```

#### stdlib_base_modf( x, integral, frac )

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

```c
double integral;
double frac;

stdlib_base_modf( 4.0, &integral, &frac );
```

The function accepts the following arguments:

-   **x**: `[in] double` input value.
-   **integral**: `[out] double*` destination for the integral part.
-   **frac**: `[out] double*` destination for the fractional part.

```c
void stdlib_base_modf( const double x, double *integral, double *frac );
```

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

int main( void ) {
    const double x[] = { 4.0, 0.0, -0.0, 1.0, -1.0, 3.14, -3.14, 1.0e308, -1.0e308, 1.0/0.0, -1.0/0.0, 0.0/0.0 };

    double integral;
    double frac;
    int i;
    for ( i = 0; i < 12; i++ ) {
        stdlib_base_modf( x[ i ], &integral, &frac );
        printf( "x: %lf => integral: %lf, frac: %lf\n", x[ i ], integral, frac );
    }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

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

<section class="related">

</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">

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

</section>

<!-- /.links -->
