On 2017-01-19 17:44, William Stein wrote:
On Thu, Jan 19, 2017 at 9:39 AM, Jeroen Demeyer <jdeme...@cage.ugent.be> wrote:
On 2017-01-19 17:17, William Stein wrote:
... and presumably what we already decided is now completely
impossible to implement and banned from Python3?
I don't think we ever decided anything. For Parents, we use Robert
Bradshaw's implementation from 2008 but it's not documented what it does or
why it does things that way. For example, there is a doctest
sage: ZZ < QQ
True
but I doubt that this is the right thing to do.
Let me rewrite the above: ... and presumably what we already
**implemented** is now completely
impossible to implement and banned from Python3?
It's mostly possible. However, what's the point of trying to reverse
engineer the current code when it probably doesn't do the right thing?
Since we have to change comparison code anyway for Python 3, we should
use this opportunity to properly define how comparison should work.
Secondly, Python 3 has different "best practices" for comparison
compared to Python 2. Example:
Python 2.7.5:
>>> 1 < "x"
True
Python 3.4.1:
>>> 1 < "x"
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unorderable types: int() < str()
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