gistfile1.hs

module Main where

main = run tests where
	run [] = putStrLn "no tests to run"
	run [x] = x
	run (x:xs) = x >> sep >> run xs

tests = [
	myConcatTest,
	concatManyTest,
	myReverseTest,
	sliceTest,
	removeAtTest
	]

sep = putStrLn "---------------------"

myConcat :: [a] -> [a] -> [a]
myConcat left right = rec left right
	where
		rec [] [] = []
		rec [] (x:xs) = x : rec [] xs
		rec (x:xs) right = x : rec xs right

myConcatTest :: IO ()
myConcatTest = do
	print $ myConcat "abc" "def"

concatMany :: [[a]] -> [a]
concatMany list = rec list []
	where
		rec :: [[a]] -> [a] -> [a]
		rec [] acc = acc
		rec (x:xs) acc = rec xs (myConcat acc x)

concatManyTest :: IO ()
concatManyTest = do
	print $ concatMany ["abc", "def", "ghi"]

myReverse :: [a] -> [a]
myReverse list = rec list []
	where
		rec [] acc = acc
		rec (x:xs) acc = rec xs (x:acc)

myReverseTest :: IO ()
myReverseTest = do
	print $ myReverse "abcd"

slice :: Int -> Int -> [a] -> [a]
slice start len list = rec start len list
	where
		rec 0 0 _ = []
		rec _ _ [] = []
		rec 0 len (x:xs) = x : rec 0 (len-1) xs
		rec start len (x:xs) = rec (start-1) len xs

sliceTest :: IO ()
sliceTest = do
	print $ slice 1 1 [1, 2, 3]
	print $ slice 4 3 "abcdefghijklm"

removeAt :: Int -> [a] -> (a, [a])
removeAt 0 (x:xs) = (x, xs)
removeAt i list = rec i list []
	where
		rec 0 (x:xs) acc = (x, myReverse $ myConcat xs acc)
		rec i (x:xs) acc = rec (i-1) xs (x:acc)

removeAtTest :: IO ()
removeAtTest = do
	print $ removeAt 1 "abc"
	print $ removeAt 2 [1, 2, 3, 4]