# compute-gcd

Computes the greatest common divisor (gcd).

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compute-gcd
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Greatest Common Divisor
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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``