# bitwise-enum
Efficient sets over bounded enumerations, using bitwise operations based on [containers](https://hackage.haskell.org/package/containers-0.6.0.1/docs/src/Data.IntSet.Internal.html) and [EdisonCore](https://hackage.haskell.org/package/EdisonCore-1.3.2.1/docs/src/Data-Edison-Coll-EnumSet.html). All operations apart from folds are constant-time. In many cases, the compiler may use constant folding to optimize `EnumSet`s away entirely. For example, in the following code:
```hs
import Data.Enum.Set as E
data Foo = A | B | C | D | E | F | G | H deriving (Bounded, Enum, Eq, Ord)
instance E.AsEnumSet Foo
addFoos :: E.EnumSet Foo -> E.EnumSet Foo
addFoos = E.delete A . E.insert B
bar :: E.EnumSet Foo
bar = addFoos $ E.fromFoldable [A, C, E]
barHasA :: Bool
barHasA = E.member A bar
```
With -O or -O2 , `bar` will compile to `GHC.Types.W# 22##` and `barHasA` will compile to `GHC.Types.False`.
By default, `Word`s are used as the representation. Other representations may be chosen in the class instance:
```hs
{-# LANGUAGE TypeFamilies #-}
import Data.Enum.Set as E
import Data.Word (Word64)
data Foo = A | B | C | D | E | F | G | H deriving (Bounded, Enum, Eq, Ord, Show)
instance E.AsEnumSet Foo where
type EnumSetRep Foo = Word64
```