@stdlib/number-float64-base-to-words

Split a double-precision floating-point number into a higher order word and a lower order word.

Usage no npm install needed!

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README

Words

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Split a double-precision floating-point number into a higher order word and a lower order word.

Installation

npm install @stdlib/number-float64-base-to-words

Usage

var toWords = require( '@stdlib/number-float64-base-to-words' );

toWords( [out,] x )

Splits a double-precision floating-point number into a higher order word (unsigned 32-bit integer) and a lower order word (unsigned 32-bit integer).

var w = toWords( 3.14e201 );
// returns [ 1774486211, 2479577218 ]

By default, the function returns an array containing two elements: a higher order word and a lower order word. The lower order word contains the less significant bits, while the higher order word contains the more significant bits and includes the exponent and sign.

var w = toWords( 3.14e201 );
// returns [ 1774486211, 2479577218 ]

var high = w[ 0 ];
// returns 1774486211

var low = w[ 1 ];
// returns 2479577218

To avoid unnecessary memory allocation, the function supports providing an output (destination) object.

var Uint32Array = require( '@stdlib/array-uint32' );

var out = new Uint32Array( 2 );

var w = toWords( out, 3.14e201 );
// returns <Uint32Array>[ 1774486211, 2479577218 ]

var bool = ( w === out );
// returns true

Examples

var floor = require( '@stdlib/math-base-special-floor' );
var randu = require( '@stdlib/random-base-randu' );
var pow = require( '@stdlib/math-base-special-pow' );
var toWords = require( '@stdlib/number-float64-base-to-words' );

var frac;
var exp;
var w;
var x;
var i;

// Generate random numbers and split into words...
for ( i = 0; i < 100; i++ ) {
    frac = randu() * 10.0;
    exp = -floor( randu()*324.0 );
    x = frac * pow( 10.0, exp );
    w = toWords( x );
    console.log( 'x: %d. higher: %d. lower: %d.', x, w[ 0 ], w[ 1 ] );
}

C APIs

Usage

#include "stdlib/number/float64/base/to_words.h"

stdlib_base_float64_to_words( x, *high, *low )

Splits a double-precision floating-point number into a higher order word and a lower order word.

#include <stdint.h>

uint32_t high;
uint32_t low;

stdlib_base_float64_to_words( 3.14, &high, &low );

The function accepts the following arguments:

  • x: [in] double input value.
  • high: [out] uint32_t* destination for higher order word.
  • low: [out] uint32_t* destination for lower order word.
void stdlib_base_float64_to_words( const double x, uint32_t *high, uint32_t *low );

stdlib_base_float64_words_t

An opaque type definition for a union for converting between a double-precision floating-point number and two unsigned 32-bit integers.

#include <stdint.h>

stdlib_base_float64_words_t w;

// Assign a double-precision floating-point number:
w.value = 3.14;

// Extract the high and low words:
uint32_t high = w.words.high;
uint32_t low = w.words.low;

The union has the following members:

  • value: double double-precision floating-point number.

  • words: struct struct having the following members:

    • high: uint32_t higher order word.
    • low: uint32_t lower order word.

Examples

#include "stdlib/number/float64/base/to_words.h"
#include <stdint.h>
#include <stdio.h>

int main() {
    double x[] = { 3.14, -3.14, 0.0, 0.0/0.0 };

    uint32_t high;
    uint32_t low;
    int i;
    for ( i = 0; i < 4; i++ ) {
        stdlib_base_float64_to_words( x[ i ], &high, &low );
        printf( "%lf => high: %u, low: %u\n", x[ i ], high, low );
    }
}

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.

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License

See LICENSE.

Copyright

Copyright © 2016-2022. The Stdlib Authors.