When is an empty container contained by a non-empty container?
For example:
{} in {1:'a', 'b':2] <-- TypeError because of hashability
set() in {1, 2, 'a', 'b'} <-- ditto
[] in ['a', 'b', 1, 2] <-- False
'' in 'a1b2' <-- True
SomeFlag.nothing in SomeFlag.something <-- ???
Personally, I have never had a use for '' in 'some string' being True, and always have to guard against that scenario.
Likewise, if an empty collection of flags is contained by a collection of flags, then that will trip me up as well; on
the other hand, it seems that collections of related flags are often treated as in set theory, where the empty set is a
member of any non-empty set...
So, does Flag adhere to set theory, or is just happenstance that some operators
work the same for both groups?
Can we have `SomeFlag.nothing in SomeFlag.something` be `False`, or would that
be too surprising?
--
~Ethan~
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