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# gcd

> Compute the [greatest common divisor][gcd] (gcd).

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The [greatest common divisor][gcd] (gcd) of two non-zero integers `a` and `b` is the largest positive integer which divides both `a` and `b` without a remainder. The gcd is also known as the **greatest common factor** (gcf), **highest common factor** (hcf), **highest common divisor**, and **greatest common measure** (gcm).

</section>

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<section class="usage">

## Usage

```javascript
var gcd = require( '@stdlib/math/base/special/gcd' );
```

#### gcd( a, b )

Computes the [greatest common divisor][gcd] (gcd).

```javascript
var v = gcd( 48, 18 );
// returns 6
```

If both `a` and `b` are `0`, the function returns `0`.

```javascript
var v = gcd( 0, 0 );
// returns 0
```

Both `a` and `b` must have integer values; otherwise, the function returns `NaN`.

```javascript
var v = gcd( 3.14, 18 );
// returns NaN

v = gcd( 48, 3.14 );
// returns NaN

v = gcd( NaN, 18 );
// returns NaN

v = gcd( 48, NaN );
// returns NaN
```

</section>

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</section>

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## Examples

<!-- eslint no-undef: "error" -->

```javascript
var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var gcd = require( '@stdlib/math/base/special/gcd' );

var a;
var b;
var v;
var i;

for ( i = 0; i < 100; i++ ) {
    a = round( randu()*50.0 );
    b = round( randu()*50.0 );
    v = gcd( a, b );
    console.log( 'gcd(%d,%d) = %d', a, b, v );
}
```

</section>

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## References

-   Stein, Josef. 1967. "Computational problems associated with Racah algebra." _Journal of Computational Physics_ 1 (3): 397–405. doi:[10.1016/0021-9991(67)90047-2][@stein:1967].

</section>

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<section class="links">

[gcd]: http://en.wikipedia.org/wiki/Greatest_common_divisor

[@stein:1967]: https://doi.org/10.1016/0021-9991(67)90047-2

</section>

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