[Python-ideas] constant/enum type in stdlib

[drekin at gmail.com]

Hello. It should be also possible to specify the values of enum constants explicitly. For 'bitmask' type only powers of 2 should be allowed or maybe the values could be the exponents (as your TypeFlag example indicates).

The same way 'symbolic' type acts as str and 'sequential' type acts as int, 'bitmask' type could act both as int and set (or frozenset) since its semantics is like of set. The enum value object could represent both the int value and corresponding singleton set. OR-ing would produce corresponding multivalue set.

>>> isinstance(TypeFlag.HEAPTYPE, int)
True
>>> isinstance(TypeFlag.HEAPTYTE, set)
True

>>> TypeFlag.HAS_GC | TypeFlag.INT_SUBCLASS
TypeFlag.HEAPTYPE|HAS_GS # or maybe <TypeFlag {HEAPTYPE, HAS_GS}>
>>> TypeFlag.HEAPTYPE in (TypeFlag.HEAPTYPE | TypeFlag.HAS_GC)
True
>>> TypeFlag.HEAPTYPE in TypeFlag.HEAPTYPE
True

>>> TypeFlag(1)
TypeFlag.HEAPTYPE
>>> TypeFlag(2)
TypeFlag.HAS_GC
>>> set(TypeFlag.HEAPTYPE)
{1}
>>> set(TypeFlag.HEAPTYPE | TypeFlag.HAS_GC)
{1, 2}
>>> int(TypeFlag.HEAPTYPE)
2
>>> int(TypeFlag.HEAPTYPE | TypeFlag.HAS_GC)
6

Note the difference between n and 2 ** n semantics. So there slould be something like
>>> TypeFlag.decompose(2)
TypeFlag.HEAPTYPE
>>> TypeFlag.decompose(6)
TypeFlag.HEAPTYPE|HAS_GS


Regards, Drekin