https://github.com/stdlib-js/math-base-special-frexpf

Split a single-precision floating-point number into a normalized fraction and an integer power of two.
https://github.com/stdlib-js/math-base-special-frexpf

dbl denormalized double float float64 floating-point frexp frexpf ieee754 javascript math mathematics node node-js nodejs normal normalized number stdlib subnormal

Last synced: 6 months ago
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Split a single-precision floating-point number into a normalized fraction and an integer power of two.

Host: GitHub
URL: https://github.com/stdlib-js/math-base-special-frexpf
Owner: stdlib-js
License: apache-2.0
Created: 2025-06-13T14:15:30.000Z (8 months ago)
Default Branch: main
Last Pushed: 2025-06-14T06:28:41.000Z (8 months ago)
Last Synced: 2025-06-24T10:25:29.759Z (7 months ago)
Topics: dbl, denormalized, double, float, float64, floating-point, frexp, frexpf, ieee754, javascript, math, mathematics, node, node-js, nodejs, normal, normalized, number, stdlib, subnormal
Language: JavaScript
Homepage: https://github.com/stdlib-js/stdlib
Size: 271 KB
Stars: 0
Watchers: 0
Forks: 0
Open Issues: 0
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Code of conduct: CODE_OF_CONDUCT.md
- Citation: CITATION.cff
- Security: SECURITY.md

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# frexpf

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

> Split a [single-precision floating-point number][ieee754] into a normalized fraction and an integer power of two.

## Installation

```bash

npm install @stdlib/math-base-special-frexpf

```

Alternatively,

-   To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).

-   If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).

-   For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).

The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

## Usage

```javascript

var frexpf = require( '@stdlib/math-base-special-frexpf' );

```

#### frexpf( x )

Splits a [single-precision floating-point number][ieee754] into a normalized fraction and an integer power of two.

```javascript

var out = frexpf( 4.0 );

// returns [ 0.5, 3 ]

```

By default, the function returns the normalized fraction and the exponent as a two-element `array`. The normalized fraction and exponent satisfy the relation `x = frac * 2^exp`.

```javascript

var pow = require( '@stdlib/math-base-special-pow' );

var x = 4.0;

var out = frexpf( x );

// returns [ 0.5, 3 ]

var frac = out[ 0 ];

var exp = out[ 1 ];

var bool = ( x === frac * pow(2.0, exp) );

// returns true

```

If provided positive or negative zero, `NaN`, or positive or negative `infinity`, the function returns a two-element `array` containing the input value and an exponent equal to `0`.

```javascript

var out = frexpf( 0.0 );

// returns [ 0.0, 0 ]

out = frexpf( -0.0 );

// returns [ -0.0, 0 ]

out = frexpf( NaN );

// returns [ NaN, 0 ]

out = frexpf( Infinity );

// returns [ Infinity, 0 ]

out = frexpf( -Infinity );

// returns [ -Infinity, 0 ]

```

For all other numeric input values, the [absolute value][@stdlib/math/base/special/absf] of the normalized fraction resides on the interval `[0.5,1)`.

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

Splits a [single-precision floating-point number][ieee754] into a normalized fraction and an integer power of two and assigns results to a provided output array.

```javascript

var Float32Array = require( '@stdlib/array-float32' );

var out = new Float32Array( 2 );

var y = frexpf.assign( 4.0, out, 1, 0 );

// returns [ 0.5, 3 ]

var bool = ( y === out );

// returns true

```

## Notes

-   Care should be taken when reconstituting a [single-precision floating-point number][ieee754] from a normalized fraction and an exponent. For example,

    ```javascript

    var pow = require( '@stdlib/math-base-special-pow' );

    var f32 = require( '@stdlib/number-float64-base-to-float32' );

    var x = 1.7014118346046923e+38; // x ~ 2^127

    var out = frexpf( x );

    // returns [ 0.5, 128 ]

    // Naive reconstitution:

    var y = f32( out[ 0 ] * f32( pow( 2.0, out[ 1 ] ) ) );

    // returns Infinity

    // Account for 2^128 evaluating as infinity by recognizing 2^128 = 2^1 * 2^127:

    y = f32( out[ 0 ] * f32( pow( 2.0, out[1]-127 ) ) * f32( pow( 2.0, 127 ) ) );

    // returns 1.7014118346046923e+38

    ```

## Examples

```javascript

var randu = require( '@stdlib/random-base-randu' );

var roundf = require( '@stdlib/math-base-special-roundf' );

var pow = require( '@stdlib/math-base-special-pow' );

var f32 = require( '@stdlib/number-float64-base-to-float32' );

var BIAS = require( '@stdlib/constants-float32-exponent-bias' );

var frexpf = require( '@stdlib/math-base-special-frexpf' );

var sign;

var frac;

var exp;

var x;

var f;

var v;

var i;

// Generate random numbers and break each into a normalized fraction and an integer power of two...

for ( i = 0; i < 100; i++ ) {

    if ( randu() < 0.5 ) {

        sign = f32( -1.0 );

    } else {

        sign = f32( 1.0 );

    }

    frac = f32( randu()*10.0 );

    exp = roundf( randu()*76.0 ) - 38;

    x = f32( sign * frac * f32( pow( 10.0, exp ) ) );

    f = frexpf( x );

    if ( f[ 1 ] > BIAS ) {

        v = f32( f[ 0 ] * f32( pow(2.0, f[1]-BIAS) ) * f32( pow(2.0, BIAS) ) );

    } else {

        v = f32( f[ 0 ] * f32( pow( 2.0, f[ 1 ] ) ) );

    }

    console.log( '%d = %d * 2^%d = %d', x, f[ 0 ], f[ 1 ], v );

}

```

* * *

## C APIs

### Usage

```c

#include "stdlib/math/base/special/frexpf.h"

```

#### stdlib_base_frexpf( x, frac, exp )

Splits a [single-precision floating-point number][ieee754] into a normalized fraction and an integer power of two.

```c

#include 

float frac;

int32_t exp;

stdlib_base_frexpf( 4.0f, &frac, &exp );

```

The function accepts the following arguments:

-   **x**: `[in] float` input value.

-   **frac**: `[out] float*` destination for the normalized fraction.

-   **exp**: `[out] int32_t*` destination for the integer power of two.

```c

void stdlib_base_frexpf( const float x, float *frac, int32_t *exp );

```

### Examples

```c

#include "stdlib/math/base/special/frexpf.h"

#include 

#include 

#include 

int main( void ) {

    const float x[] = { 4.0f, 0.0f, -0.0f, 1.0f, -1.0f, 3.14f, -3.14f, 1.0e38f, -1.0e38f, 1.0f/0.0f, -1.0f/0.0f, 0.0f/0.0f };

    float frac;

    int32_t exp;

    int i;

    for ( i = 0; i < 12; i++ ) {

        stdlib_base_frexpf( x[i], &frac, &exp );

        printf( "x: %f => frac: %f, exp: %" PRId32 "\n", x[i], frac, exp );

    }

}

```

* * *

## 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 © 2016-2025. The Stdlib [Authors][stdlib-authors].

[npm-image]: http://img.shields.io/npm/v/@stdlib/math-base-special-frexpf.svg

[npm-url]: https://npmjs.org/package/@stdlib/math-base-special-frexpf

[test-image]: https://github.com/stdlib-js/math-base-special-frexpf/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/math-base-special-frexpf/actions/workflows/test.yml?query=branch:main

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/math-base-special-frexpf/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/math-base-special-frexpf?branch=main

[chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg

[chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im

[stdlib]: https://github.com/stdlib-js/stdlib

[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors

[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-frexpf/tree/deno

[deno-readme]: https://github.com/stdlib-js/math-base-special-frexpf/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/math-base-special-frexpf/tree/umd

[umd-readme]: https://github.com/stdlib-js/math-base-special-frexpf/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/math-base-special-frexpf/tree/esm

[esm-readme]: https://github.com/stdlib-js/math-base-special-frexpf/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/math-base-special-frexpf/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/math-base-special-frexpf/main/LICENSE

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

[@stdlib/math/base/special/absf]: https://github.com/stdlib-js/math-base-special-absf

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