[Python-bugs-list] [ python-Bugs-444510 ] int() should guarantee truncation

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Bugs item #444510, was opened at 2001-07-25 09:03
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Category: Python Interpreter Core
Group: None
Status: Closed
Resolution: Fixed
Priority: 5
Submitted By: Guido van Rossum (gvanrossum)
Assigned to: Tim Peters (tim_one)
Summary: int() should guarantee truncation

Initial Comment:
The int() function currently warns that it cannot
guarantee truncation because C doesn't guarantee it. 
However, all known (to us) C implementations *do*
truncate, and the C99 standard requires it, so we might
as well change the code to promise truncation and
tighten the docs.

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>Comment By: Guido van Rossum (gvanrossum)
Date: 2001-07-26 13:24

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I don't know if you worry that what you coded now is slower,
but a config-time test could determine whether it's
necessary.

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Comment By: Tim Peters (tim_one)
Date: 2001-07-26 13:19

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Like your commodities salesman is required to tell you, 
past behavior is no guarantee of future performance.  Heck, 
for all I know, the Cray T3E may not truncate -- don't know 
whether they ever *got* that far in the test suite.  If you 
want a guarantee, you need code that makes it so regardless.

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Comment By: Guido van Rossum (gvanrossum)
Date: 2001-07-26 13:10

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Cool.  But if that test proved it, why bother change the
code?

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Comment By: Tim Peters (tim_one)
Date: 2001-07-26 13:05

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Truncation now guaranteed.

Doc/lib/libfuncs.tex; new revision: 1.81
Lib/test/test_b1.py; new revision: 1.36
Objects/floatobject.c; new revision: 2.83

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Comment By: Tim Peters (tim_one)
Date: 2001-07-26 12:51

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Assigned to me.

BTW, note that I wasn't guessing about the behavior of "all 
known Python platforms":  Python's test_b1.py has been 
checking all along that int(float) truncates, so if there 
were a platform where that didn't happen, we would have 
heard about it.


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