@stdlib/math-base-special-frexp

Split a double-precision floating-point number into a normalized fraction and an integer power of two.

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

Science Score: 44.0%

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Keywords

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

Last synced: 4 months ago · JSON representation ·

Repository

Split a double-precision floating-point number into a normalized fraction and an integer power of two.

Basic Info

Host: GitHub
Owner: stdlib-js
License: apache-2.0
Language: JavaScript
Default Branch: main
Homepage: https://github.com/stdlib-js/stdlib
Size: 829 KB

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Stars: 2
Watchers: 3
Forks: 0
Open Issues: 0
Releases: 0

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

Created over 4 years ago · Last pushed 4 months ago

Metadata Files

Readme Changelog Contributing License Code of conduct Citation Security

We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.

The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.

When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.

To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!

frexp

$NPM version$ $Build Status$ $Coverage Status$

Split a double-precision floating-point number into a normalized fraction and an integer power of two.

## Installation ```bash npm install @stdlib/math-base-special-frexp ``` 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 frexp = require( '@stdlib/math-base-special-frexp' ); ``` #### frexp( x ) Splits a [double-precision floating-point number][ieee754] into a normalized fraction and an integer power of two. ```javascript var out = frexp( 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 = frexp( 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 = frexp( 0.0 ); // returns [ 0.0, 0 ] out = frexp( -0.0 ); // returns [ -0.0, 0 ] out = frexp( NaN ); // returns [ NaN, 0 ] out = frexp( Infinity ); // returns [ Infinity, 0 ] out = frexp( -Infinity ); // returns [ -Infinity, 0 ] ``` For all other numeric input values, the [absolute value][@stdlib/math/base/special/abs] of the normalized fraction resides on the interval `[0.5,1)`. #### frexp.assign( x, out, stride, offset ) Splits a [double-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 Float64Array = require( '@stdlib/array-float64' ); var out = new Float64Array( 2 ); var y = frexp.assign( 4.0, out, 1, 0 ); // returns [ 0.5, 3 ] var bool = ( y === out ); // returns true ```

## Notes - Care should be taken when reconstituting a [double-precision floating-point number][ieee754] from a normalized fraction and an exponent. For example, ```javascript var pow = require( '@stdlib/math-base-special-pow' ); var x = 8.988939926493918e+307; // x ~ 2^1023 var out = frexp( x ); // returns [ 0.5000263811533315, 1024 ] // Naive reconstitution: var y = out[ 0 ] * pow( 2.0, out[ 1 ] ); // returns Infinity // Account for 2^1024 evaluating as infinity by recognizing 2^1024 = 2^1 * 2^1023: y = out[ 0 ] * pow( 2.0, out[1]-1023 ) * pow( 2.0, 1023 ); // returns 8.988939926493918e+307 ```

## Examples ```javascript var randu = require( '@stdlib/random-base-randu' ); var round = require( '@stdlib/math-base-special-round' ); var pow = require( '@stdlib/math-base-special-pow' ); var BIAS = require( '@stdlib/constants-float64-exponent-bias' ); var frexp = require( '@stdlib/math-base-special-frexp' ); 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 = -1.0; } else { sign = 1.0; } frac = randu() * 10.0; exp = round( randu()*616.0 ) - 308; x = sign * frac * pow( 10.0, exp ); f = frexp( x ); if ( f[ 1 ] > BIAS ) { v = f[ 0 ] * pow( 2.0, f[1]-BIAS ) * pow( 2.0, BIAS ); } else { v = f[ 0 ] * 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/frexp.h" ``` #### stdlib_base_frexp( x, frac, exp ) Splits a [double-precision floating-point number][ieee754] into a normalized fraction and an integer power of two. ```c #include double frac; int32_t exp; stdlib_base_frexp( 4.0, &frac, &exp ); ``` The function accepts the following arguments: - **x**: `[in] double` input value. - **frac**: `[out] double*` destination for the normalized fraction. - **exp**: `[out] int32_t*` destination for the integer power of two. ```c void stdlib_base_frexp( const double x, double *frac, int32_t *exp ); ```

### Examples ```c #include "stdlib/math/base/special/frexp.h" #include #include #include 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 frac; int32_t exp; int i; for ( i = 0; i < 12; i++ ) { stdlib_base_frexp( 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].

Owner

Name: stdlib
Login: stdlib-js
Kind: organization

Website: https://stdlib.io
Twitter: stdlibjs
Repositories: 3,692
Profile: https://github.com/stdlib-js

Standard library for JavaScript.

Citation (CITATION.cff)

cff-version: 1.2.0
title: stdlib
message: >-
  If you use this software, please cite it using the
  metadata from this file.

type: software

authors:
  - name: The Stdlib Authors
    url: https://github.com/stdlib-js/stdlib/graphs/contributors

repository-code: https://github.com/stdlib-js/stdlib
url: https://stdlib.io

abstract: |
  Standard library for JavaScript and Node.js.

keywords:
  - JavaScript
  - Node.js
  - TypeScript
  - standard library
  - scientific computing
  - numerical computing
  - statistical computing

license: Apache-2.0 AND BSL-1.0

date-released: 2016

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npmjs.org: @stdlib/math-base-special-frexp

Split a double-precision floating-point number into a normalized fraction and an integer power of two.

Homepage: https://stdlib.io
License: Apache-2.0
Latest release: 0.2.3
published over 1 year ago

Versions: 14
Dependent Packages: 9
Dependent Repositories: 9
Downloads: 195 Last month

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Downloads: 4.3%

Average: 8.1%

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Maintainers (4)

planeshifter rreusser stdlib-bot kgryte

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@stdlib/math-base-special-frexp

Science Score: 44.0%

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