Result of ``a is b''
ark at acm.org
Wed Mar 17 02:54:46 CET 2004
"Axel Boldt" <axelboldt at yahoo.com> wrote in message
news:40200384.0403161255.7fca7a8c at posting.google.com...
> Wow. So it seems that the action of "is" on immutables is unspecified
> and implementation dependent, thus useless to the programmer.
Hardly. It has two fundamental properties, which can sometimes be useful:
1) If x and y refer to the same object, "x is y" yields True.
2) If "x is y" yields True, "x==y" also yields True. Equivalently, if
"x==y" yields False, "x is y" also yields False.
> Maybe one could redefine "is" on immutables as follows: for strings
> and numbers it acts as "==", for tuples it acts as componentwise "is".
> That would be a more useful operator IMHO.
Can you give a realistic example of code that would benefit from such a
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