mathjs/test/function/combinatorics/stirlingS2.test.js

Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser and offers an integrated solution to work with numbers, big numbers, complex numbers, units, and matrices.

var assert = require('assert'),
error = require('../../../lib/error/index'),
math = require('../../../index'),
stirlingS2 = math.stirlingS2;

describe('stirlingS2', function() {

  it('should calculate the number of ways to partition a set of n objects into k non-empty subsets', function() {
    assert.equal(stirlingS2(5,3), 25);
    assert.equal(stirlingS2(0,0), 1);
    assert.equal(stirlingS2(8,7), 28);
  });

  it('should calculate the stirlingS2 of n items taken k at a time with BigNumbers', function(){
    assert.deepEqual(stirlingS2(math.bignumber(7), math.bignumber(5)),math.bignumber(140));
    assert.deepEqual(stirlingS2(math.bignumber(8), math.bignumber(6)),math.bignumber(266));
  });

  it('should not work with non-integer and negative input', function() {
    assert.throws(function() {stirlingS2(0.5, 3)}, TypeError);
    assert.throws(function() {stirlingS2(3, 5)}, TypeError);
    assert.throws(function() {stirlingS2(math.bignumber(3), math.bignumber(5))}, TypeError);
    assert.throws(function() {stirlingS2(math.bignumber(3.5), math.bignumber(-3))}, TypeError);
    assert.throws(function() {stirlingS2(math.bignumber(3.5), 1/3)}, TypeError);
  });

  it('should not work with the wrong number or type of arguments', function() {
    assert.throws(function() {stirlingS2(5, 3, 2)});
    assert.throws(function() {stirlingS2(true, "hello world")});
  });

  it('should LaTeX stirlingS2', function () {
    var expression = math.parse('stirlingS2(3,2)');
    assert.equal(expression.toTex(), '\\mathrm{S}\\left(3,2\\right)');
  });

});