@stdlib/math-base-special-ldexp

What is @stdlib/math-base-special-ldexp?

@stdlib/math-base-special-ldexp is a specialized npm package that provides a function to multiply a number by an integer power of two. This is useful in various mathematical computations, particularly in floating-point arithmetic and scientific calculations.

What are @stdlib/math-base-special-ldexp's main functionalities?

Multiply a number by an integer power of two

This feature allows you to multiply a floating-point number by 2 raised to the power of an integer. In this example, 1.5 is multiplied by 2^3, resulting in 12.

const ldexp = require('@stdlib/math-base-special-ldexp');
const result = ldexp(1.5, 3);
console.log(result); // 12

Other packages similar to @stdlib/math-base-special-ldexp

mathjs

mathjs is a comprehensive math library for JavaScript and Node.js. It provides a wide range of mathematical functions, including basic arithmetic, algebra, statistics, and more. While it does not have a direct equivalent to ldexp, it offers extensive functionality for various mathematical operations.

big.js

big.js is a library for arbitrary-precision decimal arithmetic. It is useful for applications requiring high precision in mathematical calculations. Although it does not specifically provide an ldexp function, it offers precise control over arithmetic operations, which can be useful in similar contexts.

decimal.js

decimal.js is another library for arbitrary-precision decimal arithmetic. It provides a wide range of mathematical functions and operations with high precision. Like big.js, it does not have an ldexp function but offers extensive capabilities for precise arithmetic.

README

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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

Notes

• This function is the inverse of frexp.

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;

for ( i = 0; i < 100; i++ ) {
    if ( randu() < 0.5 ) {
        sign = -1.0;
    } else {
        sign = 1.0;
    }
    // Generate a random number:
    frac = randu() * 10.0;
    exp = round( randu()*616.0 ) - 308;
    x = sign * frac * pow( 10.0, exp );

    // Break the number into a normalized fraction and an integer power of two:
    f = frexp( x );

    // Reconstitute the original number:
    v = ldexp( f[ 0 ], f[ 1 ] );
    console.log( '%d = %d * 2^%d = %d', x, f[ 0 ], f[ 1 ], v );
}

---

C APIs

Usage

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

stdlib_base_ldexp( frac, exp )

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

double x = stdlib_base_ldexp( 0.5, 3 ); // => 0.5 * 2^3 = 0.5 * 8
// returns 4.0

The function accepts the following arguments:

• frac: [in] double input value.
• exp: [in] int32_t integer power of two.

double stdlib_base_ldexp( const double frac, const int32_t exp );

Examples

#include "stdlib/math/base/special/ldexp.h"
#include "stdlib/math/base/special/frexp.h"
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <inttypes.h>
#include <math.h>

static double rand_double() {
    int r = rand();
    return (double)r / ( (double)RAND_MAX + 1.0 );
}

int main( void ) {
    double sign;
    double frac;
    int32_t exp;
    double x;
    double v;
    int i;

    for ( i = 0; i < 100; i++ ) {
        if ( rand_double() < 0.5 ) {
            sign = -1.0;
        } else {
            sign = 1.0;
        }
        // Generate a random number:
        frac = rand_double() * 10.0;
        exp = (int32_t)( rand_double()*616.0 ) - 308;
        x = sign * frac * pow( 10.0, exp );

        // Break the number into a normalized fraction and an integer power of two:
        stdlib_base_frexp( x, &frac, &exp );

        // Reconstitute the original number:
        v = stdlib_base_ldexp( frac, exp );

        printf( "%e = %lf * 2^%" PRId32 " = %e\n", x, frac, exp, v );
    }
}

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See Also

• @stdlib/math-base/special/frexp: split a double-precision floating-point number into a normalized fraction and an integer power of two.

---

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

---

License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.

Changelog

0.2.3 (2024-07-28)

<section class="commits">

Commits

<details>

• 55ec8ed - docs: remove comment (by Athan Reines)
• 2777e4b - bench: resolve lint errors in benchmarks (by Athan Reines)
• d04dcbd - docs: remove private annotations in C comments (by Philipp Burckhardt)
• 41d41e9 - test: include trailing newlines in Julia-generated JSON fixtures (by Philipp Burckhardt)
• 9ed7d0e - chore: add missing trailing newlines (by Philipp Burckhardt)

</details> </section> <!-- /.commits --> <section class="contributors">

Contributors

A total of 2 people contributed to this release. Thank you to the following contributors:

• Athan Reines
• Philipp Burckhardt

</section> <!-- /.contributors --> </section> <!-- /.release --> <section class="release" id="v0.2.2">