22 lines
631 B
Haskell
22 lines
631 B
Haskell
module Logic.Statement where
|
|
|
|
import Data.Set (singleton, union, toAscList)
|
|
|
|
data Statement
|
|
= Atom String
|
|
| Not Statement
|
|
| And Statement Statement
|
|
| Or Statement Statement
|
|
| Implies Statement Statement
|
|
| Iff Statement Statement
|
|
deriving (Show, Eq)
|
|
|
|
atoms :: Statement -> [String]
|
|
atoms = toAscList . mkSet
|
|
where
|
|
mkSet (Atom key) = singleton key
|
|
mkSet (Not s) = mkSet s
|
|
mkSet (And s1 s2) = union (mkSet s1) (mkSet s2)
|
|
mkSet (Or s1 s2) = union (mkSet s1) (mkSet s2)
|
|
mkSet (Implies s1 s2) = union (mkSet s1) (mkSet s2)
|
|
mkSet (Iff s1 s2) = union (mkSet s1) (mkSet s2)
|