Greatest Common Divisor

Computes the greatest common divisor (gcd).

Note: the gcd is also known as the greatest common factor (gcf), highest common factor (hcf), highest common divisor, and greatest common measure (gcm).

Installation

$ npm install compute-gcd

For use in the browser, use browserify.

Usage

var gcd = require( 'compute-gcd' );

gcd( a, b[, c,...,n] )

Computes the greatest common divisor (gcd) of two or more integers.

var val = gcd( 48, 18 );
// returns 6

var val = gcd( 8, 12, 16 );
// returns 4

gcd( arr[, accessor] )

Computes the greatest common divisor (gcd) of two or more integers.

var val = gcd( [48, 18] );
// returns 6

var val = gcd( [8, 12, 16] );
// returns 4

For object arrays, provide an accessor function for accessing array values

var data = [
	['beep', 4],
	['boop', 8],
	['bap', 12],
	['baz', 16]
];

function getValue( d, i ) {
	return d[ 1 ];
}

var arr = gcd( arr, getValue );
// returns 4

Notes

For more than 3 values, a performance gain can be achieved if the values are sorted in ascending order.
If provided an array with a length less than 2 or a single integer argument, the function returns null.

Examples

var gcd = require( 'compute-gcd' );

// Compute the gcd of random tuples...
var x, y, z, arr, val;
for ( var i = 0; i < 100; i++ ) {
	x = Math.round( Math.random()*50 );
	y = Math.round( Math.random()*50 );
	z = Math.round( Math.random()*50 );
	arr = [ x, y, z ];
	val = gcd( arr );
	console.log( arr, val );
}

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

$ node ./examples/index.js

Tests

Unit

Unit tests use the Mocha test framework with Chai assertions. 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

License

MIT license.

compute-io / gcd