30 lines
1.2 KiB
Haskell
30 lines
1.2 KiB
Haskell
module Ternary.Statement (Statement(..), st) where
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import Ternary.Term (Vee, Term(..), Item(..))
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data Statement a = A a a -- Affirmo (general affirmative)
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| I a a -- affIrmo (private affirmative)
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| E a a -- nEgo (general negative)
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| O a a -- negO (private negative)
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| A' a a
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| I' a a
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| E' a a
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| O' a a
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deriving (Eq, Show, Read)
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inv :: (Eq a) => Term a -> Term a
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inv (Term p x) = Term (not p) x
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i :: (Eq a) => Bool -> Term a -> Term a -> Vee a
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i v x y
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| x == inv y = error "x and not x under the same Vee, refusing to calculate"
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| x /= y = Term v . Item $ [x, y]
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| x == y = Term v . Item $ [x]
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st :: (Eq a) => Statement a -> Vee a
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st (A x y) = i False (Term True x) (Term False y)
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st (I x y) = i True (Term True x) (Term True y)
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st (E x y) = i False (Term True x) (Term True y)
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st (O x y) = i True (Term True x) (Term False y)
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st (A' x y) = i False (Term False x) (Term False y)
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st (I' x y) = i True (Term False x) (Term True y)
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st (E' x y) = i False (Term False x) (Term True y)
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st (O' x y) = i True (Term False x) (Term False y)
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