@stdlib/number-float64-base-set-low-word
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    0.0.6 • Public • Published

    Set Low Word

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    Set the less significant 32 bits of a double-precision floating-point number.

    Installation

    npm install @stdlib/number-float64-base-set-low-word

    Usage

    var setLowWord = require( '@stdlib/number-float64-base-set-low-word' );

    setLowWord( x, low )

    Sets the less significant 32 bits (lower order word) of a double-precision floating-point number x to a bit sequence represented by an unsigned 32-bit integer low. The returned double will have the same more significant 32 bits (higher order word) as x.

    var low = 5 >>> 0; // => 00000000000000000000000000000101
    
    var x = 3.14e201; // => 0 11010011100 01001000001011000011 10010011110010110101100010000010
    
    var y = setLowWord( x, low ); // => 0 11010011100 01001000001011000011 00000000000000000000000000000101
    // returns 3.139998651394392e+201

    Setting the lower order bits of NaN or positive or negative infinity will return NaN, as NaN is defined as a double whose exponent bit sequence is all ones and whose fraction can be any bit sequence except all zeros. Positive and negative infinity are defined as doubles with an exponent bit sequence equal to all ones and a fraction equal to all zeros. Hence, changing the less significant bits of positive and negative infinity converts each value to NaN.

    var PINF = require( '@stdlib/constants-float64-pinf' );
    var NINF = require( '@stdlib/constants-float64-ninf' );
    
    var low = 12345678;
    
    var y = setLowWord( PINF, low );
    // returns NaN
    
    y = setLowWord( NINF, low );
    // returns NaN
    
    y = setLowWord( NaN, low );
    // returns NaN

    Examples

    var pow = require( '@stdlib/math-base-special-pow' );
    var round = require( '@stdlib/math-base-special-round' );
    var randu = require( '@stdlib/random-base-randu' );
    var MAX_UINT32 = require( '@stdlib/constants-uint32-max' );
    var setLowWord = require( '@stdlib/number-float64-base-set-low-word' );
    
    var frac;
    var exp;
    var low;
    var x;
    var y;
    var i;
    
    // Generate a random double-precision floating-point number:
    frac = randu() * 10.0;
    exp = -round( randu() * 323.0 );
    x = frac * pow( 10.0, exp );
    
    // Replace the lower order word of `x` to generate new random numbers having the same higher order word...
    for ( i = 0; i < 100; i++ ) {
        low = round( randu()*MAX_UINT32 );
        y = setLowWord( x, low );
        console.log( 'x: %d. new low word: %d. y: %d.', x, low, y );
    }

    C APIs

    Usage

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

    stdlib_base_float64_set_low_word( low, *x )

    Sets the less significant 32 bits of a double-precision floating-point number.

    #include <stdint.h>
    
    uint32_t low = 1374389537;
    double x = 3.14;
    
    stdlib_base_float64_set_low_word( low, &x );

    The function accepts the following arguments:

    • low: [in] uint32_t lower order word.
    • x: [in-out] double* reference to (and destination for) a double-precision floating-point number.
    void stdlib_base_float64_set_low_word( const uint32_t low, double *x );

    Examples

    #include "stdlib/number/float64/base/set_low_word.h"
    #include <stdint.h>
    #include <stdio.h>
    
    int main() {
        uint32_t low[] = { 1374389535, 1374389545, 1374389555, 1374389565 };
        double x = 3.14;
    
        int i;
        for ( i = 0; i < 4; i++ ) {
            stdlib_base_float64_set_low_word( low[ i ], &x );
            printf( "low: %u => %.15lf\n", low[ i ], x );
        }
    }

    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.

    Install

    npm i @stdlib/number-float64-base-set-low-word

    Homepage

    stdlib.io

    DownloadsWeekly Downloads

    23,100

    Version

    0.0.6

    License

    Apache-2.0

    Unpacked Size

    56 kB

    Total Files

    16

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