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@chuck0523
Created April 6, 2016 23:24
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import Graphics.Element exposing (show)
import Graphics.Collage exposing (collage, filled, move, ngon)
import Color exposing (green, purple)
import List exposing (filter)
-- list length(http://elm-lang.org/examples/length)
-- main =
-- show (length [1..9]) -- 9
length : List a -> Int
length list =
case list of
[] ->
0
first :: rest ->
1 + length rest
-- zip(http://elm-lang.org/examples/zip)
-- main =
-- show (zip ["Tom", "Sue", "Bob"] [45, 31, 26]) -- [("Tom",45),("Sue",31),("Bob",26)]
zip : List a -> List b -> List (a, b)
zip xs xy =
case (xs, xy) of
(x :: xs', y :: ys') ->
(x, y) :: zip xs' ys'
(_, _) ->
[]
-- quick-sort(http://elm-lang.org/examples/quick-sort)
-- main =
-- show (quicksort [5, 3, 8, 1, 9, 4, 7]) -- [1,3,4,5,7,8,9]
quicksort : List comparable -> List comparable
quicksort list =
case list of
[] ->
[]
pivot :: rest ->
let
lower = filter (\n -> n <= pivot) rest
higher = filter (\n -> n > pivot) rest
in
quicksort lower ++ [pivot] ++ quicksort higher
-- merge-sort(http://elm-lang.org/examples/merge-sort)
main =
show (mergesort[5, 3, 8, 1, 9, 4, 7]) -- [1,3,4,5,7,8,9]
mergesort : List comparable -> List comparable
mergesort list =
case list of
[] ->
list
[_] ->
list
_ ->
let
(xs, ys) = split list
in
merge (mergesort xs) (mergesort ys)
split : List a -> (List a, List a)
split list =
case list of
[] ->
([], [])
x :: rest ->
let
(xs, ys) = split rest
in
(ys, x :: xs)
merge : List comparable -> List comparable -> List comparable
merge xs ys =
case (xs, ys) of
(x :: xs', y :: ys') ->
if x < y
then x :: merge xs' ys
else y :: merge xs ys'
([], rest) ->
rest
(rest, []) ->
rest
-- main =
-- show (isEven 2, filter isEven [1..9]) -- (True,[2,4,6,8])
isEven : Int -> Bool
isEven int =
int % 2 == 0
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