23 lines
697 B
Haskell
23 lines
697 B
Haskell
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module Ternary.Universum (Universum(..), universum, aFromStatements) where
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import Data.List (nub)
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import Ternary.Term (Item (..), Term (..), Vee)
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data Universum = Aristotle
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| Empty
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| Default
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universum :: (Eq a) => Universum -> [Vee a] -> [Vee a]
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universum Aristotle facts =
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[Term True (Item [Term x v])
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| v <- aFromStatements facts,
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x <- [False, True]]
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universum Empty _ = []
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universum Default xs = xs
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aFromStatements :: (Eq a) => [Vee a] -> [a]
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aFromStatements = nub . concatMap (extract . getItem . getVee)
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where
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getItem (Item x) = x
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getVee (Term _ i) = i
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extract terms = [v | (Term _ v) <- terms]
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