Re: [Haskell-cafe] [C][enums][newbie] What is natural Haskell representation of such enum?

2012/1/22 Данило Глинський What is natural Haskell representation of such enum?

enum TypeMask { UNIT, GAMEOBJECT,

CREATURE_OR_GAMEOBJECT = UNIT | GAMEOBJECT };

I don't think that definition makes any sense in C, because UNIT is 0, so UNIT | GAMEOBJECT == GAMEOBJECT == 1 Nevertheless, in Haskell something vaguely similar might be: data TypeMask = UNIT | GAMEOBJECT | CREATURE_OR_GAMEOBJECT

// 1-byte flaged enum enum TypeMask { // ... UNIT = 0x0004, GAMEOBJECT = 0x0008, // ...

CREATURE_OR_GAMEOBJECT = UNIT | GAMEOBJECT WORLDOBJECT = UNIT | PLAYER | GAMEOBJECT | DYNAMICOBJECT | CORPSE // ... even more enum combos ... };

import Data.Bits data TypeMask = UNIT | GAMEOBJECT | CREATURE_OR_GAMEOBJECT | WORLDOBJECT instance Enum TypeMask where fromEnum UNIT = 0x4 fromEnum GAMEOBJECT = 0x8 fromEnum CREATURE_OR_GAMEOBJECT = fromEnum UNIT .|. fromEnum GAMEOBJECT fromEnum WORLDOBJECT = fromEnum UNIT .|. fromEnum PLAYER .|. fromEnum GAMEOBJECT .|. fromEnum DYNAMICOBJECT .|. fromEnum CORPSE toEnum 0x4 = UNIT toEnum 0x8 = GAMEOBJECT toEnum _ = error "unspecified enumeration value of type TypeMask" isCreatureOrGameObject :: Int -> Bool isCreatureOrGameObject x = (x .|. fromEnum CREATURE_OR_GAMEOBJECT) /= 0 isWorldObject :: Int -> Bool isWorldObject x = (x .|. fromEnum WORLDOBJECT) /= 0 -- But fundamentally, this is not an idiomatic Haskell way of doing things. -- The other posts in this thread have shown more Haskell-ish translations.