35 lines
1.1 KiB
Haskell
35 lines
1.1 KiB
Haskell
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module Ternary.Term (Term(..), Item(..), Vee) where
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import Data.List (concatMap, null, (++), (\\))
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import Prelude (Applicative, Bool (False, True), Eq, Functor,
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Read, Show, String, fmap, map, pure, show,
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(&&), (/=), (<*>), (==), (||))
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data Term a = Term Bool a deriving (Read)
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newtype Item a = Item [a] deriving (Read)
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type Vee a = Term (Item (Term a))
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instance Functor Item where
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fmap f (Item a) = Item (map f a)
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instance Applicative Item where
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pure x = Item [x]
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(Item fs) <*> (Item xs) = Item [f x | f <- fs, x <- xs]
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instance (Eq a) => Eq (Item a) where
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(Item x) == (Item y) = null dxy && null dyx
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where
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dxy = x \\ y
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dyx = y \\ x
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instance (Eq a) => Eq (Term a) where
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Term v x == Term w y = (v==w) && (x==y)
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Term v x /= Term w y = (v/=w) || (x/=y)
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instance Show (Term String) where
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show (Term False y) = y ++ "`"
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show (Term True y) = y
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instance Show (Term (Item (Term String))) where
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show (Term x i) = show (Term x "V") ++ concatMap show (it i)
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where it (Item ii) = ii
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