@stdlib/math-base-special-gcd/README.md

Compute the greatest common divisor (gcd).

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# gcd

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

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<section class="intro">

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="installation">

## Installation

```bash
npm install @stdlib/math-base-special-gcd
```

</section>

<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 class="notes">

</section>

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<section class="examples">

## Examples

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

```javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var gcd = require( '@stdlib/math-base-special-gcd' );

var a = discreteUniform( 100, 0, 50 );
var b = discreteUniform( a.length, 0, 50 );

var i;
for ( i = 0; i < a.length; i++ ) {
    console.log( 'gcd(%d,%d) = %d', a[ i ], b[ i ], gcd( a[ i ], b[ i ] ) );
}
```

</section>

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* * *

<section class="c">

## C APIs

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</section>

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<section class="usage">

### Usage

```c
#include "stdlib/math/base/special/gcd.h"
```

#### stdlib_base_gcd( a, b )

Computes the greatest common divisor (gcd).

```c
double v = stdlib_base_gcd( 48.0, 18.0 );
// returns 6.0
```

The function accepts the following arguments:

-   **a**: `[in] double` input value.
-   **b**: `[in] double` input value.

```c
double stdlib_base_gcd( const double a, const double b );
```

</section>

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<section class="notes">

</section>

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<section class="examples">

### Examples

```c
#include "stdlib/math/base/special/gcd.h"
#include <stdio.h>

int main( void ) {
    const double a[] = { 24.0, 32.0, 48.0, 116.0, 33.0 };
    const double b[] = { 12.0, 6.0, 15.0, 52.0, 22.0 };

    double out;
    int i;
    for ( i = 0; i < 5; i++ ) {
        out = stdlib_base_gcd( a[ i ], b[ i ] );
        printf( "gcd(%lf, %lf) = %lf\n", a[ i ], b[ i ], out );
    }
}
```

</section>

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</section>

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<section class="references">

## 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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* * *

## See Also

-   <span class="package-name">[`@stdlib/math-base/special/lcm`][@stdlib/math/base/special/lcm]</span><span class="delimiter">: </span><span class="description">compute the least common multiple (lcm).</span>

</section>

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<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

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## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2024. The Stdlib [Authors][stdlib-authors].

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

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

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