On 4/22/2015 8:45 PM, Guido van Rossum wrote:
On Wed, Apr 22, 2015 at 2:38 PM, Chris Barker <[email protected]
<mailto:[email protected]>> wrote:
On Tue, Apr 21, 2015 at 11:32 PM, Terry Reedy <[email protected]
<mailto:[email protected]>> wrote:
I was just thinking today that for this, typing needs a
subtraction (difference) operation in addition to an addition
(union) operation: Difference(Iterable(str), str)
Anyway, the point is that being able to say "all these types, except
this one" would solve this particular problem -- but would it solve
any others? Do we want this to work around a quirk in Pythons string
type?
More seriously, I doubt there are other important use cases for Difference.
I thought about Difference(numbers.Number, complex) to get ordered
numbers, but numbers.Real should probably work. I agree more real uses
are needed before adding Difference.
--
Terry Jan Reedy
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