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{-# LANGUAGE TypeFamilies #-}
module ColInference where
type family Elem c
type instance Elem [e] = e
class Col c where
isEmpty :: c -> Bool
add :: c -> Elem c -> c
headTail :: c -> (Elem c,c)
addAll :: (Col c1, Col c2, Elem c1 ~ Elem c2) => c1 -> c2 -> c2
addAll c1 c2
| isEmpty c1
= c2
| otherwise
= let (x,c1') = headTail c1
in addAll c1' (add c2 x)
|
