time-to-botec/squiggle/node_modules/@stdlib/math/base/special/imuldw/README.md

imuldw

Compute the double word product of two signed 32-bit integers.

Usage

var imuldw = require( '@stdlib/math/base/special/imuldw' );

imuldw( [out,] a, b )

Multiplies two signed 32-bit integers and returns an array of two signed 32-bit integers which represents the signed 64-bit integer product.

var v = imuldw( 1, 10 );
// returns [ 0, 10 ]

v = imuldw( 0x80000000|0, 0x40000000|0 ); // -(2^31) * 2^30 = -2305843009213694000 => 32-bit integer overflow
// returns [ -536870912, 0 ]

Notes

• When computing the product of 32-bit integer values in double-precision floating-point format (the default JavaScript numeric data type), computing the double word product is necessary in order to avoid exceeding the maximum safe double-precision floating-point integer value.

Examples

var lpad = require( '@stdlib/string/left-pad' );
var imuldw = require( '@stdlib/math/base/special/imuldw' );

var i;
var j;
var y;

for ( i = 0x7FFFFFF0; i < 0x7FFFFFFF; i++ ) {
    for ( j = i; j < 0x7FFFFFFF; j++) {
        y = imuldw( i|0, j|0 );
        console.log( '%d x %d = 0x%s%s', i|0, j|0, lpad( ( y[0] >>> 0 ).toString( 16 ), 8, '0'), lpad( ( y[1] >>> 0 ).toString( 16 ), 8, '0' ) );
    }
}