time-to-botec

Benchmark sampling in different programming languages
Log | Files | Refs | README

main.js (2149B)

      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 getWord = require( './../../../../float32/base/to-word' );
     24 var BIAS = require( '@stdlib/constants/float32/exponent-bias' );
     25 
     26 
     27 // VARIABLES //
     28 
     29 // Exponent mask: 0 11111111 00000000000000000000000
     30 var EXP_MASK = 0x7f800000; // TODO: consider making an external constant
     31 
     32 
     33 // MAIN //
     34 
     35 /**
     36 * Returns an integer corresponding to the unbiased exponent of a single-precision floating-point number.
     37 *
     38 * @param {number} x - single-precision floating-point number
     39 * @returns {integer8} unbiased exponent
     40 *
     41 * @example
     42 * var toFloat32 = require( '@stdlib/number/float64/base/to-float32' );
     43 * var exp = exponentf( toFloat32( 3.14e34 ) ); // => 2**114 ~ 2.08e34
     44 * // returns 114
     45 *
     46 * @example
     47 * var toFloat32 = require( '@stdlib/number/float64/base/to-float32' );
     48 * var exp = exponentf( toFloat32( 3.14e-34 ) ); // => 2**-112 ~ 1.93e-34
     49 * // returns -112
     50 *
     51 * @example
     52 * var toFloat32 = require( '@stdlib/number/float64/base/to-float32' );
     53 * var exp = exponentf( toFloat32( -3.14 ) );
     54 * // returns 1
     55 *
     56 * @example
     57 * var exp = exponentf( 0.0 );
     58 * // returns -127
     59 *
     60 * @example
     61 * var exp = exponentf( NaN );
     62 * // returns 128
     63 */
     64 function exponentf( x ) {
     65 	// Convert `x` to an unsigned 32-bit integer corresponding to the IEEE 754 binary representation:
     66 	var w = getWord( x );
     67 
     68 	// Apply a mask to isolate only the exponent bits and then shift off all bits which are part of the fraction:
     69 	w = ( w & EXP_MASK ) >>> 23;
     70 
     71 	// Remove the bias and return:
     72 	return w - BIAS;
     73 }
     74 
     75 
     76 // EXPORTS //
     77 
     78 module.exports = exponentf;