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Some small clarifications based on c.l.py feedback. Added open issue 

about __truediv__ vs. __div__ in Python 3.0.
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Guido van Rossum 2001-07-29 23:05:12 +00:00
parent 220e3da93f
commit 3ea05fba23
1 changed files with 16 additions and 5 deletions
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pep-0238.txt
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@ -171,7 +171,7 @@ Alternatives
operations, the int and the float value could be miles apart, operations, the int and the float value could be miles apart,
it's unclear which value should be used in comparisons, and of it's unclear which value should be used in comparisons, and of
course many contexts (like conversion to string) don't have a course many contexts (like conversion to string) don't have a
clear integer or float context. clear integer or float preference.
- Use a directive to use specific division semantics in a module, - Use a directive to use specific division semantics in a module,
rather than a future statement. This retains classic division rather than a future statement. This retains classic division
@ -293,7 +293,7 @@ Semantics of Floor Division
3.5//2.0 == 1.0 3.5//2.0 == 1.0
For complex numbers, // raises an exception, since float() of a For complex numbers, // raises an exception, since floor() of a
complex number is not allowed. complex number is not allowed.
For user-defined classes and extension types, all semantics are up For user-defined classes and extension types, all semantics are up
@ -338,6 +338,10 @@ The Future Division Statement
Open Issues Open Issues
We expect that these issues will be resolved over time, as more
feedback is received or we gather more experience with the initial
implementation.
- It has been proposed to call // the quotient operator, and the / - It has been proposed to call // the quotient operator, and the /
operator the ratio operator. I'm not sure about this -- for operator the ratio operator. I'm not sure about this -- for
some people quotient is just a synonym for division, and ratio some people quotient is just a synonym for division, and ratio
@ -362,6 +366,12 @@ Open Issues
the interim, maybe the long-to-float conversion could be made to the interim, maybe the long-to-float conversion could be made to
raise OverflowError if the long is out of range. raise OverflowError if the long is out of range.
- For classes to have to support all three of __div__(),
__floordiv__() and __truediv__() seems painful; and what to do
in 3.0? Maybe we only need __div__() and __floordiv__(), or
maybe at least true division should try __truediv__() first and
__div__() second.
FAQ FAQ
@ -389,9 +399,10 @@ FAQ
while the documentation of int() says that int() can round or while the documentation of int() says that int() can round or
truncate depending on the C implementation, we know of no C truncate depending on the C implementation, we know of no C
implementation that doesn't truncate, and we're going to change implementation that doesn't truncate, and we're going to change
the spec for int() to promise truncation. Note that for the spec for int() to promise truncation. Note that classic
negative ints, classic division (and floor division) round division (and floor division) round towards negative infinity,
towards negative infinity, while int() rounds towards zero. while int() rounds towards zero, giving different answers for
negative numbers.
Q. How do I specify the division semantics for input(), compile(), Q. How do I specify the division semantics for input(), compile(),
execfile(), eval() and exec? execfile(), eval() and exec?