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# npm

## @stdlib/math-base-special-ldexp 0.0.6 • Public • Published

# ldexp

Multiply a double-precision floating-point number by an integer power of two.

## Installation

`npm install @stdlib/math-base-special-ldexp`

## Usage

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

#### ldexp( frac, exp )

Multiplies a double-precision floating-point number by an `integer` power of two; i.e., `x = frac * 2^exp`.

```var x = ldexp( 0.5, 3 ); // => 0.5 * 2^3 = 0.5 * 8
// returns 4.0

x = ldexp( 4.0, -2 ); // => 4 * 2^(-2) = 4 * (1/4)
// returns 1.0```

If `frac` equals positive or negative `zero`, `NaN`, or positive or negative `infinity`, the function returns a value equal to `frac`.

```var x = ldexp( 0.0, 20 );
// returns 0.0

x = ldexp( -0.0, 39 );
// returns -0.0

x = ldexp( NaN, -101 );
// returns NaN

x = ldexp( Infinity, 11 );
// returns Infinity

x = ldexp( -Infinity, -118 );
// returns -Infinity```

## Examples

```var randu = require( '@stdlib/random-base-randu' );
var round = require( '@stdlib/math-base-special-round' );
var pow = require( '@stdlib/math-base-special-pow' );
var frexp = require( '@stdlib/math-base-special-frexp' );
var ldexp = require( '@stdlib/math-base-special-ldexp' );

var sign;
var frac;
var exp;
var x;
var f;
var v;
var i;

/*
* 1) Generate random numbers.
* 2) Break each number into a normalized fraction and an integer power of two.
* 3) Reconstitute the original number.
*/
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 );
v = ldexp( f[ 0 ], f[ 1 ] );
console.log( '%d = %d * 2^%d = %d', x, f[ 0 ], f[ 1 ], v );
}```

## Notice

This package is part of 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, see the main project repository.

#### Community ## Keywords

### Install

`npm i @stdlib/math-base-special-ldexp`

### Repository

github.com/stdlib-js/math-base-special-ldexp

stdlib.io

100,713

0.0.6