On Thu, 2021-05-27 at 20:24 -0700, 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? >
Maybe something like the following would be a good starting point: @bitmask_require_individual_bits -- Best regards, Michał Górny _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/PPPCZGMDH47UPGH6RKVXNQQX3IQ2AMCS/ Code of Conduct: http://python.org/psf/codeofconduct/
