powm1

Computes bˣ - 1.

When b is close to 1 and/or x is small, this implementation is more accurate than naively computing bˣ minus 1.

Installation

$ npm install math-powm1

Usage

var powm1 = require( 'math-powm1' );

powm1( b, x )

Computes bˣ - 1.

var y = powm1( 2, 3 );
// returns 7
 
y = powm1( 4, 0.5 );
// returns 1
 
y = powm1( 0, 100 );
// returns -1
 
y = powm1( 100, 0 );
// returns 0
 
y = powm1( 0, 0 );
// returns 0
 
y = powm1( Math.PI, 5 );
// returns ~305.0197
 
y = powm1( NaN, 3 );
// returns NaN
 
y = powm1( 5, NaN );
// returns NaN

Examples

var powm1 = require( 'math-powm1' );
 
var b;
var x;
var y;
var i;
 
for ( i = 0; i < 100; i++ ) {
    b = Math.round( Math.random()*10 );
    x = Math.round( Math.random()*10 ) - 5;
    y = powm1( b, x );
    console.log( '%d^%d - 1 = %d', b, x, y );
}

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.