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* @license Apache-2.0
*
* Copyright (c) 2018 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
// MODULES //
var SIGN_MASK = require( '@stdlib/constants/float64/high-word-sign-mask' );
var toWords = require( '@stdlib/number/float64/base/to-words' );
var getHighWord = require( '@stdlib/number/float64/base/get-high-word' );
var fromWords = require( '@stdlib/number/float64/base/from-words' );
// VARIABLES //
// High/low words workspace:
var WORDS = [ 0>>>0, 0>>>0 ]; // asm type annotation
// MAIN //
/**
* Returns a double-precision floating-point number with the magnitude of `x` and the sign of `x*y`.
*
* @param {number} x - number from which to derive a magnitude
* @param {number} y - number from which to derive a sign
* @returns {number} a double-precision floating-point number
*
* @example
* var z = flipsign( -3.0, 10.0 );
* // returns -3.0
*
* @example
* var z = flipsign( -3.0, -1.0 );
* // returns 3.0
*
* @example
* var z = flipsign( 1.0, -0.0 );
* // returns -1.0
*
* @example
* var z = flipsign( -3.0, -0.0 );
* // returns 3.0
*
* @example
* var z = flipsign( -0.0, 1.0 );
* // returns -0.0
*
* @example
* var z = flipsign( 0.0, -1.0 );
* // returns -0.0
*/
function flipsign( x, y ) {
var hx;
var hy;
// Split `x` into higher and lower order words:
toWords.assign( x, WORDS, 1, 0 );
hx = WORDS[ 0 ];
// Extract the higher order word from `y`:
hy = getHighWord( y );
// Leave only the sign bit of `y` turned on (if on):
hy &= SIGN_MASK;
// Flip the sign bit of `x` only when the sign bit of `y` is on:
hx ^= hy; // 1^1=0 (flipped), 0^1=1 (flipped), 1^0=1 (unchanged), 0^0=0 (unchanged)
// Return a new value having the same magnitude as `x`, but with the sign of `x*y`:
return fromWords( hx, WORDS[ 1 ] );
}
// EXPORTS //
module.exports = flipsign;
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