math-float64-ldexp v1.0.1
ldexp
Multiplies a double-precision floating-point number by an integer power of two.
Installation
$ npm install math-float64-ldexp
Usage
var ldexp = require( 'math-float64-ldexp' );
ldexp( frac, exp )
Multiplies a double-precision floating-point number by an integer
power of two; i.e., x = frac * 2**exp
.
var x = ldexp( 0.5, 3 ); // => 0.5 * 2**3 = 0.5 * 8
// returns 4
x = ldexp( 4, -2 ); // => 4 * 2**(-2) = 4 * (1/4)
// returns 1
If frac
equals positive or negative zero
, NaN
, or positive or negative infinity
, the function
returns a value equal to frac
.
var x = ldexp( 0, 20 );
// returns 0
x = ldexp( -0, 39 );
// returns -0
x = ldexp( NaN, -101 );
// returns NaN
x = ldexp( Number.POSITIVE_INFINITY, 11 );
// returns +infinity
x = ldexp( Number.NEGATIVE_INFINITY, -118 );
// returns -infinity
Notes
- This
function
is the inverse offrexp
.
Examples
var round = require( 'math-round' );
var pow = require( 'math-power' );
var frexp = require( 'math-float64-frexp' );
var ldexp = require( 'math-float64-ldexp' );
var sign;
var frac;
var exp;
var x;
var f;
var v;
var i;
/**
* 1) Generate random numbers.
* 2) Break each number into a normalized fraction and an integer power of two.
* 3) Reconstitute the original number.
*/
for ( i = 0; i < 100; i++ ) {
if ( Math.random() < 0.5 ) {
sign = -1;
} else {
sign = 1;
}
frac = Math.random() * 10;
exp = round( Math.random()*616 ) - 308;
x = sign * frac * pow( 10, exp );
f = frexp( x );
v = ldexp( f[ 0 ], f[ 1 ] );
console.log( '%d = %d * 2^%d = %d', x, f[ 0 ], f[ 1 ], v );
}
To run the example code from the top-level application directory,
$ node ./examples/index.js
Tests
Unit
This repository uses tape for unit tests. To run the tests, execute the following command in the top-level application directory:
$ make test
All new feature development should have corresponding unit tests to validate correct functionality.
Test Coverage
This repository uses Istanbul as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:
$ make test-cov
Istanbul creates a ./reports/coverage
directory. To access an HTML version of the report,
$ make view-cov
Browser Support
This repository uses Testling for browser testing. To run the tests in a (headless) local web browser, execute the following command in the top-level application directory:
$ make test-browsers
To view the tests in a local web browser,
$ make view-browser-tests
License
Copyright
Copyright © 2016. The Compute.io Authors.