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)]