time-to-botec

Benchmark sampling in different programming languages
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copysign.js (2368B)

      1 /**
      2 * @license Apache-2.0
      3 *
      4 * Copyright (c) 2018 The Stdlib Authors.
      5 *
      6 * Licensed under the Apache License, Version 2.0 (the "License");
      7 * you may not use this file except in compliance with the License.
      8 * You may obtain a copy of the License at
      9 *
     10 *    http://www.apache.org/licenses/LICENSE-2.0
     11 *
     12 * Unless required by applicable law or agreed to in writing, software
     13 * distributed under the License is distributed on an "AS IS" BASIS,
     14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     15 * See the License for the specific language governing permissions and
     16 * limitations under the License.
     17 */
     18 
     19 'use strict';
     20 
     21 // MODULES //
     22 
     23 var toWords = require( '@stdlib/number/float64/base/to-words' );
     24 var getHighWord = require( '@stdlib/number/float64/base/get-high-word' );
     25 var fromWords = require( '@stdlib/number/float64/base/from-words' );
     26 
     27 
     28 // VARIABLES //
     29 
     30 // 10000000000000000000000000000000 => 2147483648 => 0x80000000
     31 var SIGN_MASK = 0x80000000>>>0; // asm type annotation
     32 
     33 // 01111111111111111111111111111111 => 2147483647 => 0x7fffffff
     34 var MAGNITUDE_MASK = 0x7fffffff|0; // asm type annotation
     35 
     36 // High/low words workspace:
     37 var WORDS = [ 0, 0 ]; // WARNING: not thread safe
     38 
     39 
     40 // MAIN //
     41 
     42 /**
     43 * Returns a double-precision floating-point number with the magnitude of `x` and the sign of `y`.
     44 *
     45 * @param {number} x - number from which to derive a magnitude
     46 * @param {number} y - number from which to derive a sign
     47 * @returns {number} a double-precision floating-point number
     48 *
     49 * @example
     50 * var z = copysign( -3.14, 10.0 );
     51 * // returns 3.14
     52 *
     53 * @example
     54 * var z = copysign( 3.14, -1.0 );
     55 * // returns -3.14
     56 *
     57 * @example
     58 * var z = copysign( 1.0, -0.0 );
     59 * // returns -1.0
     60 *
     61 * @example
     62 * var z = copysign( -3.14, -0.0 );
     63 * // returns -3.14
     64 *
     65 * @example
     66 * var z = copysign( -0.0, 1.0 );
     67 * // returns 0.0
     68 */
     69 function copysign( x, y ) {
     70 	var hx;
     71 	var hy;
     72 
     73 	// Split `x` into higher and lower order words:
     74 	toWords( WORDS, x );
     75 	hx = WORDS[ 0 ];
     76 
     77 	// Turn off the sign bit of `x`:
     78 	hx &= MAGNITUDE_MASK;
     79 
     80 	// Extract the higher order word from `y`:
     81 	hy = getHighWord( y );
     82 
     83 	// Leave only the sign bit of `y` turned on:
     84 	hy &= SIGN_MASK;
     85 
     86 	// Copy the sign bit of `y` to `x`:
     87 	hx |= hy;
     88 
     89 	// Return a new value having the same magnitude as `x`, but with the sign of `y`:
     90 	return fromWords( hx, WORDS[ 1 ] );
     91 }
     92 
     93 
     94 // EXPORTS //
     95 
     96 module.exports = copysign;