1  import functools
       2  import unittest
       3  from math import isnan, nextafter
       4  from test.support import requires_IEEE_754
       5  from test.support.hypothesis_helper import hypothesis
       6  
       7  floats = hypothesis.strategies.floats
       8  integers = hypothesis.strategies.integers
       9  
      10  
      11  def assert_equal_float(x, y):
      12      assert isnan(x) and isnan(y) or x == y
      13  
      14  
      15  def via_reduce(x, y, steps):
      16      return functools.reduce(nextafter, [y] * steps, x)
      17  
      18  
      19  class ESC[4;38;5;81mNextafterTests(ESC[4;38;5;149munittestESC[4;38;5;149m.ESC[4;38;5;149mTestCase):
      20      @requires_IEEE_754
      21      @hypothesis.given(
      22          x=floats(),
      23          y=floats(),
      24          steps=integers(min_value=0, max_value=2**16))
      25      def test_count(self, x, y, steps):
      26          assert_equal_float(via_reduce(x, y, steps),
      27                             nextafter(x, y, steps=steps))
      28  
      29      @requires_IEEE_754
      30      @hypothesis.given(
      31          x=floats(),
      32          y=floats(),
      33          a=integers(min_value=0),
      34          b=integers(min_value=0))
      35      def test_addition_commutes(self, x, y, a, b):
      36          first = nextafter(x, y, steps=a)
      37          second = nextafter(first, y, steps=b)
      38          combined = nextafter(x, y, steps=a+b)
      39          hypothesis.note(f"{first} -> {second} == {combined}")
      40  
      41          assert_equal_float(second, combined)