32 lines
1 KiB
Haskell
32 lines
1 KiB
Haskell
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module FOLSyntax where
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data Term = Var String | Fun String [Term] deriving (Eq, Ord)
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data Formula
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= Pred String [Term]
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| Neg Formula
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| Conj Formula Formula
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| Disj Formula Formula
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| Impl Formula Formula
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| All String Formula
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| Exists String Formula
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| T
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| F
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deriving (Eq, Ord)
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instance Show Term where
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show (Var x) = x
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show (Fun f []) = f
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show (Fun f (x : xs)) = f ++ "(" ++ show x ++ foldr ((++) . (", "++) . show) ")" xs
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instance Show Formula where
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show (Pred p []) = p
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show (Pred p (x : xs)) = p ++ "(" ++ show x ++ foldr ((++) . (", "++) . show) ")" xs
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show (Neg f) = "!(" ++ show f ++ ")"
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show (Conj f1 f2) = "(" ++ show f1 ++ " /\\ " ++ show f2 ++ ")"
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show (Disj f1 f2) = "(" ++ show f1 ++ " \\/ " ++ show f2 ++ ")"
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show (Impl f1 f2) = "(" ++ show f1 ++ " -> " ++ show f2 ++ ")"
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show (All x f) = "(forall " ++ x ++ ". " ++ show f ++ ")"
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show (Exists x f) = "(exists " ++ x ++ ". " ++ show f ++ ")"
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show T = "true"
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show F = "false"
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