Data commit

Task/Nested-templated-data/Haskell/nested-templated-data-1.hs

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+{-# language DeriveTraversable #-}
+
+data Template a = Val a | List [Template a]
+  deriving ( Show
+           , Functor
+           , Foldable
+           , Traversable )

Task/Nested-templated-data/Haskell/nested-templated-data-2.hs

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+subst :: (Functor t, Eq i) => [(i,a)] -> t i -> t (Maybe a)
+subst d = fmap (`lookup` d)

Task/Nested-templated-data/Haskell/nested-templated-data-3.hs

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+indexed :: [a] -> [(Int, a)]
+indexed = zip [0..]

Task/Nested-templated-data/Haskell/nested-templated-data-4.hs

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+t :: Template Int
+t = List [ List [Val 1, Val 2]
+         , List [Val 3, Val 4, Val 10]
+         , Val 5]
+
+payloads :: [(Int, String)]
+payloads = [(i, "payload#"++show i) | i <- [0..6]]

Task/Nested-templated-data/Haskell/nested-templated-data-5.hs

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+unusedIndices :: (Foldable t, Eq i) => [(i,a)] -> t i -> [i]
+unusedIndices d = foldMap unused
+  where unused i = maybe (pure i) (pure []) $ lookup i d
+
+unusedData :: (Foldable t, Eq i) => [(i, a)] -> t i -> [(i,a)]
+unusedData = foldr delete
+  where delete i = filter ((i /= ) . fst)