New submission from Mark Dickinson <[EMAIL PROTECTED]>: If n is a Python long, then one might expect float(n) to return the closest float to n. Currently it doesn't do this. For example (with Python 2.6, on OS X 10.5.2/Intel):
>>> n = 295147905179352891391L The closest float to n is equal to n+1. But float(n) returns the further of the two floats bracketing n, equal to n-65535: >>> float(n) 2.9514790517935283e+20 >>> long(float(n)) 295147905179352825856L >>> n - long(float(n)) 65535L It's fairly straightforward to fix PyLong_AsDouble to return the closest double to a given long integer n (using the round-half-to-even rule in the case of a tie). The attached patch does this. Having a correctly rounded float(n) can be useful for testing other floating-point routines that are supposed to be correctly rounded. ---------- components: Interpreter Core files: long_as_double.patch keywords: patch messages: 68545 nosy: marketdickinson severity: normal status: open title: Make conversions from long to float correctly rounded. type: feature request versions: Python 2.6 Added file: http://bugs.python.org/file10694/long_as_double.patch _______________________________________ Python tracker <[EMAIL PROTECTED]> <http://bugs.python.org/issue3166> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
