On 28. 05. 21 5:24, Ethan Furman wrote:
Greetings!
The Flag type in the enum module has had some improvements, but I find
it necessary to move one of those improvements into a decorator instead,
and I'm having a hard time thinking up a name.
What is the behavior? Well, a name in a flag type can be either
canonical (it represents one thing), or aliased (it represents two or
more things). To use Color as an example:
class Color(Flag):
RED = 1 # 0001
GREEN = 2 # 0010
BLUE = 4 # 0100
PURPLE = RED | BLUE # 0101
WHITE = RED | GREEN | BLUE # 0111
The flags RED, GREEN, and BLUE are all canonical, while PURPLE and WHITE
are aliases for certain flag combinations. But what if we have
something like:
class Color(Flag):
RED = 1 # 0001
BLUE = 4 # 0100
WHITE = 7 # 0111
As you see, WHITE is an "alias" for a value that does not exist in the
Flag (0010, or 2). That seems like it's probably an error. But what
about this?
class FlagWithMasks(IntFlag):
DEFAULT = 0x0
FIRST_MASK = 0xF
FIRST_ROUND = 0x0
FIRST_CEIL = 0x1
FIRST_TRUNC = 0x2
SECOND_MASK = 0xF0
SECOND_RECALC = 0x00
SECOND_NO_RECALC = 0x10
THIRD_MASK = 0xF00
THIRD_DISCARD = 0x000
THIRD_KEEP = 0x100
Here we have three flags (FIRST_MASK, SECOND_MASK, THIRD_MASK) that are
aliasing values that don't exist, but it seems intentional and not an
error.
So, like the enum.unique decorator that can be used when duplicate names
should be an error, I'm adding a new decorator to verify that a Flag has
no missing aliased values that can be used when the programmer thinks
it's appropriate... but I have no idea what to call it.
Any nominations?
Are you looking for a decorator for the whole Enum, or a way to mark
individual *values* as masks?
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