Bitmasks

Bitmasks for boolean flags.

Usage

Define your flags as an enumeration:

import Data.Word
import Data.Bitmask

data PizzaTopping =
    Cheese
  | Mushrooms
  | Pineapple
  | Ham
  deriving (Show, Eq, Bounded, Enum)

-- We only need 8 bits since there are only 4 toppings
type PizzaMask = Bitmask8 PizzaTopping

Creating bitmasks

-- A Margherita pizza (cheese only)
margherita :: PizzaMask
margherita = fromFlags [Cheese]

veggie :: PizzaMask
veggie = fromExceptFlags [Ham]

Access and modify flags

Use getFlag to check if a pizza has a specific topping:

>>> getFlag Cheese funghi
True
>>> getFlag Pineapple funghi
False

Add toppings to a pizza:

>>> hawaiian = addFlags [Pineapple, Ham] margherita
>>> getFlags [Pineapple, Mushroom] hawaiian
True

Make any pizza vegetarian (bitwise AND):

>>> veggieHawaiian = veggie .&. hawaiian
>>> getFlag Ham veggieHawaiian

Toggle (I have no idea what I'm talking about) the toppings :

>>> funghi = flipFlags [Pineapple, Mushroom] veggieHawaiian
>>> toFlags funghi
[Cheese,Mushrooms]

Remove a topping:

>>> margherita == deleteFlag Mushroom funghi
True

Convert to lists

-- Get all toppings as a list
>>> toFlags funghi
[Cheese,Mushrooms]
>>> toFlags hawaiian
[Cheese,Pineapple,Ham]

-- Convert to association lists
>>> toFlagsBool funghi
[(Cheese,True),(Mushrooms,True),(Pineapple,False),(Ham,False)]