math-float64-exponent

Exponent

Returns an integer corresponding to the unbiased exponent of a double-precision floating-point number.

Installation

$ npm install math-float64-exponent

Usage

var exponent = require( 'math-float64-exponent' );

exponent( x )

Returns an integer corresponding to the unbiased exponent of a double-precision floating-point number.

var exp = exponent( 3.14e307 );
// returns 1021 => 2**1021 ~ 1e307
 
var exp = exponent( 3.14e-307 );
// returns -1019 => 2**-1019 ~ 1e-307
 
exp = exponent( -3.14 );
// returns 1
 
exp = exponent( 0 );
// returns 0
 
exp = exponent( NaN );
// returns 1024 => 2**1024 ~ infinity

Examples

var round = require( 'math-round' );
var pow = require( 'math-power' );
var exponent = require( 'math-float64-exponent' );
 
var frac;
var exp;
var x;
var e;
var i;
 
// Generate random numbers and extract their exponents...
for ( i = 0; i < 100; i++ ) {
    frac = Math.random() * 10;
    exp = round( Math.random()*646 ) - 323;
    x = frac * pow( 10, exp );
    e = exponent( x );
    console.log( 'x: %d. unbiased exponent: %d.', x, e );
}

To run the example code from the top-level application directory,

$ node ./examples/index.js

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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

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License

MIT license.

Copyright

Copyright © 2016. The Compute.io Authors.