Lib/test/test_complex.py

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