From 61dff2b285249485ab2f57f7200d4c50b741c610 Mon Sep 17 00:00:00 2001 From: Tim Peters Date: Tue, 8 May 2001 15:43:37 +0000 Subject: Blurb about the increased precision of float literals in .pyc/.pyo files. --- Misc/NEWS | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/Misc/NEWS b/Misc/NEWS index f2150d5..7906613 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -3,6 +3,26 @@ What's New in Python 2.2a0? Core +- Float (and complex) literals in source code were evaluated to full + precision only when running from a .py file; the same code loaded from a + .pyc (or .pyo) file could suffer numeric differences starting at about the + 12th significant decimal digit. For example, on a machine with IEEE-754 + floating arithmetic, + + x = 9007199254740992.0 + print long(x) + + printed 9007199254740992 if run directly from .py, but 9007199254740000 + if from a compiled (.pyc or .pyo) file. This was due to marshal using + str(float) instead of repr(float) when building code objects. marshal + now uses repr(float) instead, which should reproduce floats to full + machine precision (assuming the platform C float<->string I/O conversion + functions are of good quality). + + This may cause floating-point results to change in some cases, and + usually for the better, but may also cause numerically unstable + algorithms to break. + - Dictionary objects now support the "in" operator: "x in dict" means the same as dict.has_key(x). -- cgit v0.12