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factorial

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[Factorial][factorial-function] function.

The [factorial][factorial-function] function may be defined as the product

$Factorial function definition$

--> or according to the recurrence relation Following the convention for an [empty product][empty-product], in all definitions, The [Gamma][@stdlib/math/base/special/gamma] function extends the [factorial][factorial-function] function for non-integer values. The [factorial][factorial-function] of a negative integer is not defined.

## Installation

bash
npm install @stdlib/math-base-special-factorial

## Usage

javascript
var factorial = require( '@stdlib/math-base-special-factorial' );

#### factorial( x ) Evaluates the [factorial][factorial-function] function.

javascript
var v = factorial( 3.0 );
// returns 6.0

v = factorial( -1.5 );
// returns ~-3.545

v = factorial( -0.5 );
// returns ~1.772

v = factorial( 0.5 );
// returns ~0.886

v = factorial( -10.0 );
// returns NaN

v = factorial( 171.0 );
// returns Infinity

v = factorial( NaN );
// returns NaN

## Examples

javascript
var incrspace = require( '@stdlib/array-base-incrspace' );
var factorial = require( '@stdlib/math-base-special-factorial' );

var x = incrspace( -10.0, 100.0, 1.0 );

var i;
for ( i = 0; i < x.length; i++ ) {
    console.log( 'x: %d, f(x): %d', x[ i ], factorial( x[ i ] ) );
}

## C APIs

### Usage

c
#include "stdlib/math/base/special/factorial.h"

#### stdlib_base_factorial( x ) Evaluates the [factorial][factorial-function] function.

c
double out = stdlib_base_factorial( 3.0 );
// returns 6.0

out = stdlib_base_factorial( -1.5 );
// returns ~-3.545

The function accepts the following arguments: - x: [in] double input value.

c
double stdlib_base_factorial( const double n );

### Examples

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

int main( void ) {
    const double x[] = { 2.0, 3.0, 5.0, 8.0 };

    double y;
    int i;
    for ( i = 0; i < 4; i++ ) {
        y = stdlib_base_factorial( x[ i ] );
        printf( "factorial(%lf) = %lf\n", x[ i ], y );
    }
}

* ## See Also - [@stdlib/math-base/special/factorialln][@stdlib/math/base/special/factorialln]: evaluate the natural logarithm of the factorial function.

* ## 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]. #### Community [![Chat][chat-image]][chat-url] --- ## License See [LICENSE][stdlib-license]. ## Copyright Copyright © 2016-2024. The Stdlib [Authors][stdlib-authors].

Détail du package

readme

factorial