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September 2017 Update

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This commit is contained in:
Ingy döt Net 2017-09-23 10:01:46 +02:00
parent bba7bfd280
commit ba8067c3b7
14570 changed files with 153136 additions and 63871 deletions
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34
Task/Flatten-a-list/Haskell/flatten-a-list-1.hs
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@ -1,24 +1,26 @@
import Data.Tree
import Data.Tree (Tree(..), flatten)
-- [[1], 2, [[3,4], 5], [[[]]], [[[6]]], 7, 8, []]
-- implemented as multiway tree:
-- Data.Tree represents trees where nodes have values too, unlike the trees in our problem.
-- so 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 [] [
Node [] [Node [1] []],
Node [2] [],
Node [] [
Node [] [ Node [3] [],Node [4] []],
Node [5] []
],
Node [] [Node [] [Node [] []]],
Node [] [Node [] [Node [6] []]],
Node [7] [],
Node [8] [],
Node [] []
]
list =
Node
[]
[ Node [] [Node [1] []]
, Node [2] []
, Node [] [Node [] [Node [3] [], Node [4] []], Node [5] []]
, Node [] [Node [] [Node [] []]]
, Node [] [Node [] [Node [6] []]]
, Node [7] []
, Node [8] []
, Node [] []
]
flattenList = concat.flatten
flattenList :: Tree [a] -> [a]
flattenList = concat . flatten
main :: IO ()
main = print $ flattenList list

26
Task/Flatten-a-list/Haskell/flatten-a-list-2.hs
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@ -1,16 +1,22 @@
data Tree a = Leaf a | Node [Tree a]
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 []]
main :: IO ()
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]

28
Task/Flatten-a-list/Haskell/flatten-a-list-3.hs
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@ -1,17 +1,29 @@
data NestedList a = NList [NestedList a] | Entry a
data NestedList a
= NList [NestedList a]
| Entry a
flatten :: NestedList a -> [a]
flatten nl = flatten' nl []
flatten nl = flatten_ nl []
where
-- By passing through a list which the results will be preprended to we allow efficient lazy evaluation
flatten' :: NestedList a -> [a] -> [a]
flatten' (Entry a) cont = a:cont
flatten' (NList entries) cont = foldr flatten' cont entries
flatten_ :: NestedList a -> [a] -> [a]
flatten_ (Entry a) cont = a : cont
flatten_ (NList entries) cont = foldr flatten_ cont entries
-- By passing through a list to which the results will be prepended,
-- we allow for efficient lazy evaluation
example :: NestedList Int
example = NList [ NList [Entry 1], Entry 2, NList [NList [Entry 3, Entry 4], Entry 5], NList [NList [NList []]], NList [ NList [ NList [Entry 6]]], Entry 7, Entry 8, NList []]
example =
NList
[ NList [Entry 1]
, Entry 2
, NList [NList [Entry 3, Entry 4], Entry 5]
, NList [NList [NList []]]
, NList [NList [NList [Entry 6]]]
, Entry 7
, Entry 8
, NList []
]
main :: IO ()
main = print $ flatten example
-- output [1,2,3,4,5,6,7,8]