def test_multinomial_coefficients(): assert multinomial_coefficients(1, 1) == {(1,): 1} assert multinomial_coefficients(1, 2) == {(2,): 1} assert multinomial_coefficients(1, 3) == {(3,): 1} assert multinomial_coefficients(2, 0) == {(0, 0): 1} assert multinomial_coefficients(2, 1) == {(0, 1): 1, (1, 0): 1} assert multinomial_coefficients(2, 2) == {(2, 0): 1, (0, 2): 1, (1, 1): 2} assert multinomial_coefficients(2, 3) == {(3, 0): 1, (1, 2): 3, (0, 3): 1, (2, 1): 3} assert multinomial_coefficients(3, 1) == {(1, 0, 0): 1, (0, 1, 0): 1, (0, 0, 1): 1} assert multinomial_coefficients(3, 2) == {(0, 1, 1): 2, (0, 0, 2): 1, (1, 1, 0): 2, (0, 2, 0): 1, (1, 0, 1): 2, (2, 0, 0): 1} mc = multinomial_coefficients(3, 3) assert mc == {(2, 1, 0): 3, (0, 3, 0): 1, (1, 0, 2): 3, (0, 2, 1): 3, (0, 1, 2): 3, (3, 0, 0): 1, (2, 0, 1): 3, (1, 2, 0): 3, (1, 1, 1): 6, (0, 0, 3): 1} assert dict(multinomial_coefficients_iterator(2, 0)) == {(0, 0): 1} assert dict( multinomial_coefficients_iterator(2, 1)) == {(0, 1): 1, (1, 0): 1} assert dict(multinomial_coefficients_iterator(2, 2)) == \ {(2, 0): 1, (0, 2): 1, (1, 1): 2} assert dict(multinomial_coefficients_iterator(3, 3)) == mc it = multinomial_coefficients_iterator(7, 2) assert [it.next() for i in range(4)] == \ [((2, 0, 0, 0, 0, 0, 0), 1), ((1, 1, 0, 0, 0, 0, 0), 2), ((0, 2, 0, 0, 0, 0, 0), 1), ((1, 0, 1, 0, 0, 0, 0), 2)]
def expand(self): if len(self._dict) == 1: (base, expt), = self._dict.iteritems() terms = base.terms() expansion_dict = multinomial_coefficients(len(terms), expt) return expr_from_dict(expansion_dict, terms) else: return self
def _expand1(): """multinomial_coefficients(4, 60)""" return multinomial_coefficients(4, 60)