time-to-botec

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

README.md (2835B)

      1 <!--
      2 
      3 @license Apache-2.0
      4 
      5 Copyright (c) 2018 The Stdlib Authors.
      6 
      7 Licensed under the Apache License, Version 2.0 (the "License");
      8 you may not use this file except in compliance with the License.
      9 You may obtain a copy of the License at
     10 
     11    http://www.apache.org/licenses/LICENSE-2.0
     12 
     13 Unless required by applicable law or agreed to in writing, software
     14 distributed under the License is distributed on an "AS IS" BASIS,
     15 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     16 See the License for the specific language governing permissions and
     17 limitations under the License.
     18 
     19 -->
     20 
     21 # ldexp
     22 
     23 > Multiply a [double-precision floating-point number][ieee754] by an integer power of two.
     24 
     25 <section class="usage">
     26 
     27 ## Usage
     28 
     29 ```javascript
     30 var ldexp = require( '@stdlib/math/base/special/ldexp' );
     31 ```
     32 
     33 #### ldexp( frac, exp )
     34 
     35 Multiplies a [double-precision floating-point number][ieee754] by an `integer` power of two; i.e., `x = frac * 2^exp`.
     36 
     37 ```javascript
     38 var x = ldexp( 0.5, 3 ); // => 0.5 * 2^3 = 0.5 * 8
     39 // returns 4.0
     40 
     41 x = ldexp( 4.0, -2 ); // => 4 * 2^(-2) = 4 * (1/4)
     42 // returns 1.0
     43 ```
     44 
     45 If `frac` equals positive or negative `zero`, `NaN`, or positive or negative `infinity`, the function returns a value equal to `frac`.
     46 
     47 ```javascript
     48 var x = ldexp( 0.0, 20 );
     49 // returns 0.0
     50 
     51 x = ldexp( -0.0, 39 );
     52 // returns -0.0
     53 
     54 x = ldexp( NaN, -101 );
     55 // returns NaN
     56 
     57 x = ldexp( Infinity, 11 );
     58 // returns Infinity
     59 
     60 x = ldexp( -Infinity, -118 );
     61 // returns -Infinity
     62 ```
     63 
     64 <section class="usage">
     65 
     66 <section class="notes">
     67 
     68 ## Notes
     69 
     70 -   This function is the inverse of [`frexp`][@stdlib/math/base/special/frexp].
     71 
     72 </section>
     73 
     74 <!-- /.notes -->
     75 
     76 <section class="examples">
     77 
     78 ## Examples
     79 
     80 <!-- eslint no-undef: "error" -->
     81 
     82 ```javascript
     83 var randu = require( '@stdlib/random/base/randu' );
     84 var round = require( '@stdlib/math/base/special/round' );
     85 var pow = require( '@stdlib/math/base/special/pow' );
     86 var frexp = require( '@stdlib/math/base/special/frexp' );
     87 var ldexp = require( '@stdlib/math/base/special/ldexp' );
     88 
     89 var sign;
     90 var frac;
     91 var exp;
     92 var x;
     93 var f;
     94 var v;
     95 var i;
     96 
     97 /*
     98 * 1) Generate random numbers.
     99 * 2) Break each number into a normalized fraction and an integer power of two.
    100 * 3) Reconstitute the original number.
    101 */
    102 for ( i = 0; i < 100; i++ ) {
    103     if ( randu() < 0.5 ) {
    104         sign = -1.0;
    105     } else {
    106         sign = 1.0;
    107     }
    108     frac = randu() * 10.0;
    109     exp = round( randu()*616.0 ) - 308;
    110     x = sign * frac * pow( 10.0, exp );
    111     f = frexp( x );
    112     v = ldexp( f[ 0 ], f[ 1 ] );
    113     console.log( '%d = %d * 2^%d = %d', x, f[ 0 ], f[ 1 ], v );
    114 }
    115 ```
    116 
    117 </section>
    118 
    119 <!-- /.examples -->
    120 
    121 <section class="links">
    122 
    123 [ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985
    124 
    125 [@stdlib/math/base/special/frexp]: https://www.npmjs.com/package/@stdlib/math/tree/main/base/special/frexp
    126 
    127 </section>
    128 
    129 <!-- /.links -->