mathjs/lib/function/probability/factorial.js

Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser with support for symbolic computation, comes with a large set of built-in functions and constants, and offers an integrated solution to work with dif

'use strict';

var deepMap = require('../../utils/collection/deepMap');

function factory(type, config, load, typed) {
  var gamma = load(require('./gamma'));

  var latex = require('../../utils/latex');
  /**
   * Compute the factorial of a value
   *
   * Factorial only supports an integer value as argument.
   * For matrices, the function is evaluated element wise.
   *
   * Syntax:
   *
   *    math.factorial(n)
   *
   * Examples:
   *
   *    math.factorial(5)    // returns 120
   *    math.factorial(3)    // returns 6
   *
   * See also:
   *
   *    combinations, gamma, permutations
   *
   * @param {number | BigNumber | Array | Matrix} n   An integer number
   * @return {number | BigNumber | Array | Matrix}    The factorial of `n`
   */


  var factorial = typed('factorial', {
    'number': function number(n) {
      if (n < 0) {
        throw new Error('Value must be non-negative');
      }

      return gamma(n + 1);
    },
    'BigNumber': function BigNumber(n) {
      if (n.isNegative()) {
        throw new Error('Value must be non-negative');
      }

      return gamma(n.plus(1));
    },
    'Array | Matrix': function ArrayMatrix(n) {
      return deepMap(n, factorial);
    }
  });
  factorial.toTex = {
    1: "\\left(${args[0]}\\right)".concat(latex.operators['factorial'])
  };
  return factorial;
}

exports.name = 'factorial';
exports.factory = factory;