Lib/test/test_complex.py

   1 from test_support import TestFailed
   2 from random import random
   3
   4 # These tests ensure that complex math does the right thing; tests of
   5 # the complex() function/constructor are in test_b1.py.
   6
   7 # XXX need many, many more tests here.
   8
   9 nerrors = 0
  10
  11 def check_close_real(x, y, eps=1e-9):
  12     """Return true iff floats x and y "are close\""""
  13     # put the one with larger magnitude second
  14     if abs(x) > abs(y):
  15         x, y = y, x
  16     if y == 0:
  17         return abs(x) < eps
  18     if x == 0:
  19         return abs(y) < eps
  20     # check that relative difference < eps
  21     return abs((x-y)/y) < eps
  22
  23 def check_close(x, y, eps=1e-9):
  24     """Return true iff complexes x and y "are close\""""
  25     return check_close_real(x.real, y.real, eps) and \
  26            check_close_real(x.imag, y.imag, eps)
  27
  28 def test_div(x, y):
  29     """Compute complex z=x*y, and check that z/x==y and z/y==x."""
  30     global nerrors
  31     z = x * y
  32     if x != 0:
  33         q = z / x
  34         if not check_close(q, y):
  35             nerrors += 1
  36             print "%r / %r == %r but expected %r" % (z, x, q, y)
  37     if y != 0:
  38         q = z / y
  39         if not check_close(q, x):
  40             nerrors += 1
  41             print "%r / %r == %r but expected %r" % (z, y, q, x)
  42
  43 simple_real = [float(i) for i in range(-5, 6)]
  44 simple_complex = [complex(x, y) for x in simple_real for y in simple_real]
  45 for x in simple_complex:
  46     for y in simple_complex:
  47         test_div(x, y)
  48
  49 # A naive complex division algorithm (such as in 2.0) is very prone to
  50 # nonsense errors for these (overflows and underflows).
  51 test_div(complex(1e200, 1e200), 1+0j)
  52 test_div(complex(1e-200, 1e-200), 1+0j)
  53
  54 # Just for fun.
  55 for i in range(100):
  56     test_div(complex(random(), random()),
  57              complex(random(), random()))
  58
  59 try:
  60     z = 1.0 / (0+0j)
  61 except ZeroDivisionError:
  62     pass
  63 else:
  64     nerrors += 1
  65     raise TestFailed("Division by complex 0 didn't raise ZeroDivisionError")
  66
  67 if nerrors:
  68     raise TestFailed("%d tests failed" % nerrors)