cpython/Lib/test/double_const.py
Barry Warsaw 408b6d34de Complete the absolute import patch for the test suite. All relative
imports of test modules now import from the test package.  Other
related oddities are also fixed (like DeprecationWarning filters that
weren't specifying the full import part, etc.).  Also did a general
code cleanup to remove all "from test.test_support import *"'s.  Other
from...import *'s weren't changed.
2002-07-30 23:27:12 +00:00

31 lines
1.2 KiB
Python

from test.test_support import TestFailed
# A test for SF bug 422177: manifest float constants varied way too much in
# precision depending on whether Python was loading a module for the first
# time, or reloading it from a precompiled .pyc. The "expected" failure
# mode is that when test_import imports this after all .pyc files have been
# erased, it passes, but when test_import imports this from
# double_const.pyc, it fails. This indicates a woeful loss of precision in
# the marshal format for doubles. It's also possible that repr() doesn't
# produce enough digits to get reasonable precision for this box.
PI = 3.14159265358979324
TWOPI = 6.28318530717958648
PI_str = "3.14159265358979324"
TWOPI_str = "6.28318530717958648"
# Verify that the double x is within a few bits of eval(x_str).
def check_ok(x, x_str):
assert x > 0.0
x2 = eval(x_str)
assert x2 > 0.0
diff = abs(x - x2)
# If diff is no larger than 3 ULP (wrt x2), then diff/8 is no larger
# than 0.375 ULP, so adding diff/8 to x2 should have no effect.
if x2 + (diff / 8.) != x2:
raise TestFailed("Manifest const %s lost too much precision " % x_str)
check_ok(PI, PI_str)
check_ok(TWOPI, TWOPI_str)