On 2021-05-27 at 20:23:29 -0700, Regarding "name for new Enum decorator," Ethan Furman <et...@stoneleaf.us> 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? Exhaustive? I see two qualitatively different kinds of enums: those that can/should be "or"ed together (e.g., RED, GREEN) and those that cannot (e.g., FIRST_ROUND, FIRST_CEIL, and FIRST_TRUNC). The idea of a "missing" value doesn't seem to apply to the second type (because defining FIRST_TRUNC as FIRST_ROUND | FIRST_CEIL is nonsensical). I don't quite know what that may or may not suggest as far as names go, but it may give someone else an idea. -- https://mail.python.org/mailman/listinfo/python-list
