partition.js

var { Nothing, Just } = require('sanctuary');

var R = require('../source/index.js');
var eq = require('./shared/eq.js');


describe('partition', function() {
  it('splits a list into two lists according to a predicate', function() {
    var pred = function(n) { return n % 2; };
    eq(R.partition(pred, []), [[], []]);
    eq(R.partition(pred, [0, 2, 4, 6]), [[], [0, 2, 4, 6]]);
    eq(R.partition(pred, [1, 3, 5, 7]), [[1, 3, 5, 7], []]);
    eq(R.partition(pred, [0, 1, 2, 3]), [[1, 3], [0, 2]]);
  });

  it('works with objects', function() {
    var pred = function(n) { return n % 2; };
    eq(R.partition(pred, {}), [{}, {}]);
    eq(R.partition(pred, { a: 0, b: 2, c: 4, d: 6 }),
      [{}, { a: 0, b: 2, c: 4, d: 6 }]
    );
    eq(R.partition(pred, { a: 1, b: 3, c: 5, d: 7 }),
      [{ a: 1, b: 3, c: 5, d: 7 }, {}]
    );
    eq(R.partition(pred, { a: 0, b: 1, c: 2, d: 3 }),
      [{ b: 1, d: 3 }, { a: 0, c: 2 }]
    );
  });

  it('works with other filterables', function() {
    eq(R.partition(R.isEmpty, Just(3)),
      [Nothing, Just(3)]
    );
    eq(R.partition(R.complement(R.isEmpty), Just(3)),
      [Just(3), Nothing]
    );
  });

});