npm package: @stdlib/math-base-special-modf
Description: Decompose a double-precision floating-point number into integral and fractional parts.
Author: The Stdlib Authors
Latest version: 0.3.1

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</details>

# modf

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

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

<section class="installation">

## Installation

```bash
npm install @stdlib/math-base-special-modf
```

</section>

<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 -->

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<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

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[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules

[deno-url]: https://github.com/stdlib-js/math-base-special-modf/tree/deno
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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/math-base-special-modf/main/LICENSE

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

</section>

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