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module Exercises where
-- direct recursion, not using (&&)
myAnd :: [Bool] -> Bool
myAnd [] = True
myAnd (x:xs) =
if x == False
then False
else myAnd xs
-- direct recursion, using (&&)
myAnd' :: [Bool] -> Bool
myAnd' [] = True
myAnd' (x:xs) = x && myAnd' xs
-- 1
myOr :: [Bool] -> Bool
myOr [] = False
myOr (x:xs) = x || myOr xs
-- 2
myAny :: (a -> Bool) -> [a] -> Bool
myAny f xs = myOr $ map f xs
-- 3
myElem :: Eq a => a -> [a] -> Bool
myElem _ [] = False
myElem y (x:xs) = (x == y) || (myElem y xs)
-- 4
myReverse :: [a] -> [a]
myReverse [] = []
myReverse (x:xs) = (myReverse xs) ++ [x]
-- 5
squish :: [[a]] -> [a]
squish = squish' []
where squish' acc [] = acc
squish' acc (x:xs) = x ++ (squish' acc xs)
-- 6
squishMap :: (a -> [b]) -> [a] -> [b]
squishMap _ [] = []
squishMap f (x:xs) = (f x) ++ (squishMap f xs)
-- 7
squishAgain :: [[a]] -> [a]
squishAgain x = squishMap id x
-- 8
myMaximumBy :: (a -> a -> Ordering)
-> [a] -> a
myMaximumBy f (x:xs) = myMaximumBy' x xs
where myMaximumBy' m [] = m
myMaximumBy' m (y:ys)
| f y m == GT = myMaximumBy' y ys
| otherwise = myMaximumBy' m ys
-- 9
myMinimumBy :: (a -> a -> Ordering)
-> [a] -> a
myMinimumBy f (x:xs) = myMinimumBy' x xs
where myMinimumBy' m [] = m
myMinimumBy' m (y:ys)
| f y m == LT = myMinimumBy' y ys
| otherwise = myMinimumBy' m ys
-- 10
myMaximum :: (Ord a) => [a] -> a
myMaximum = myMaximumBy compare
myMinimum :: (Ord a) => [a] -> a
myMinimum = myMinimumBy compare
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