Issue 10925: Document pure Python version of integer-to-float correctly-rounded conversion (original) (raw)

Issue10925

Created on 2011-01-17 13:00 by mark.dickinson, last changed 2022-04-11 14:57 by admin. This issue is now closed.

Messages (4)
msg126398 - (view)	Author: Mark Dickinson (mark.dickinson) *	Date: 2011-01-17 13:00
It would be helpful (perhaps to developers of alternative implementations) to give a pure Python version of correctly-rounded long-to-float conversion. Attached is such a version, as a patch to test_long in the release27-maint branch.
msg126794 - (view)	Author: Terry J. Reedy (terry.reedy) *	Date: 2011-01-21 23:28
I see there is already something similar for true division. I find + q_max, shift_max = 1 << sig_bits, sys.float_info.max_exp - sig_bits easier to read as two lines + q_max = 1 << sig_bits + shift_max = sys.float_info.max_exp - sig_bits Not having precedence memorized, I prefer added parens here: + ... (n >> shift) | bool(n & (1 << shift) - 1) I presume that for normal production testing, you would comment out + float = long_to_float
msg146177 - (view)	Author: Mark Dickinson (mark.dickinson) *	Date: 2011-10-22 18:55
Thanks for the comments. Here's an updated patch, that actually makes use of the pure Python version to test the built-in int-to-float conversion.
msg146247 - (view)	Author: Roundup Robot (python-dev)	Date: 2011-10-23 19:07
New changeset 117d51d3dd7d by Mark Dickinson in branch 'default': Issue #10925: Add equivalent pure Python code for the builtin int-to-float conversion to test_long. http://hg.python.org/cpython/rev/117d51d3dd7d