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Flatten a list: Difference between revisions
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Line 48:
-- implemented as multiway tree:
-- since Data.Tree represents trees where nodes have values too,
-- we use a list as that value, where a node will have an empty list value,
-- and a leaf will have a one-element list value and no subtrees
list :: Tree [Int]
list = Node [] [
Line 67 ⟶ 70:
<pre>*Main> flattenList list
[1,2,3,4,5,6,7,8]</pre>
Alternately:
<lang haskell>data Tree a = Leaf a | Node [Tree a]
flatten :: Tree a -> [a]
flatten (Leaf x) = [x]
flatten (Node xs) = concatMap flatten xs
main = print $ flatten $ Node [Node [Leaf 1], Leaf 2, Node [Node [Leaf 3, Leaf 4], Leaf 5], Node [Node [Node []]], Node [Node [Node [Leaf 6]]], Leaf 7, Leaf 8, Node []]
-- output: [1,2,3,4,5,6,7,8]</lang>
=={{header|J}}==
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