{-# OPTIONS_GHC -Wno-unrecognised-pragmas #-}
module Language where
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import Data.Maybe
data Expression =
EAnd (Expression,Expression)
| EOr (Expression,Expression)
| ENot Expression
| EVariable String
| EBase Bool
deriving (Ord,Eq)
expressionSize :: Expression -> Int
expressionSize (EAnd (e1,e2)) = 1+expressionSize e1+expressionSize e2
expressionSize (EOr (e1,e2)) = 1+expressionSize e1+expressionSize e2
expressionSize (ENot e) = 1+expressionSize e
expressionSize (EVariable _) = 1
expressionSize (EBase _) = 1
newtype Assignment = Assignment [(String,Bool)]
newtype Context = Context [String]
evaluate :: Assignment -> Expression -> Bool
evaluate ass (EAnd(e1,e2)) = evaluate ass e1 && evaluate ass e2
evaluate ass (EOr(e1,e2)) = evaluate ass e1 || evaluate ass e2
evaluate ass (ENot e) = not (evaluate ass e)
evaluate _ (EBase b) = b
evaluate (Assignment ctx) (EVariable s) = fromJust (lookup s ctx)
instance Show Expression where
show (EAnd (e1,e2)) = “(” ++ show e1 ++ “/\\” ++ show e2 ++ “)”
show (EOr (e1,e2)) = show e1 ++ “\\/” ++ show e2
show (ENot e) = “~(” ++ show e ++ “)”
show (EVariable s) = s
show (EBase b) = show b
typecheck :: Context -> Expression -> Bool
typecheck ctx (EAnd(e1,e2)) = typecheck ctx e1 && typecheck ctx e2
typecheck ctx (EOr(e1,e2)) = typecheck ctx e1 && typecheck ctx e2
typecheck ctx (ENot e) = typecheck ctx e
typecheck _ (EBase _) = True
typecheck (Context ctx) (EVariable s) = s `elem` ctx
newtype Examples = Examples [(Assignment,Bool)]
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