Bugs item #1681671, was opened at 2007-03-15 15:28 Message generated for change (Tracker Item Submitted) made by Item Submitter You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1681671&group_id=5470
Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Python Interpreter Core Group: Python 2.3 Status: Open Resolution: None Priority: 5 Private: No Submitted By: jehahn (jehahn) Assigned to: Nobody/Anonymous (nobody) Summary: Python and Indeterminate Forms (Math) Initial Comment: Primary example: Python 2.3.5 (#1, Mar 20 2005, 20:38:20) [GCC 3.3 20030304 (Apple Computer, Inc. build 1809)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> 0 ** 0 1 Per http://mathworld.wolfram.com/Indeterminate.html, 0 ** 0 is an indeterminate form. 0 ** 0 should probably return NaN and NOT 1. Other examples include: Python 2.3.5 (#1, Mar 20 2005, 20:38:20) [GCC 3.3 20030304 (Apple Computer, Inc. build 1809)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> inf = float("infinity") >>> inf ** 0 1.0 >>> 1 ** inf 1.0 For a few others, Python provides an arguably correct answer of NaN. Examples: Python 2.3.5 (#1, Mar 20 2005, 20:38:20) [GCC 3.3 20030304 (Apple Computer, Inc. build 1809)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> inf = float("infinity") >>> inf * 0 nan >>> inf / inf nan >>> inf - inf nan And, of course, for the most obvious indeterminate form (0/0) Python does precisely the right thing: Python 2.3.5 (#1, Mar 20 2005, 20:38:20) [GCC 3.3 20030304 (Apple Computer, Inc. build 1809)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> 0/0 Traceback (most recent call last): File "<stdin>", line 1, in ? ZeroDivisionError: integer division or modulo by zero It could be argued that the correct thing to do here is to throw an exception - mathematically speaking these forms are about as meaningful as division by zero which Python handles by throwing an exception. (unlike Java and IEEE 754, which do arguably evil things here by returning +/- infinity for the quantity k/0 for all k != 0) Unfortunately, some people doing numerical work may have gotten used to the current Python behavior so the change isn't without risk. And some of the current values are common "conventions" used to simplify certain common issues. (e.g. 0 ** 0 == 1) Moreover, I don't know if this is dependent on platform (having only tried it on a couple of the boxes I have handy.) However, from a mathematical purist's standpoint, Python is doing the wrong thing on these counts. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1681671&group_id=5470 _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
