You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
43 lines
1.1 KiB
43 lines
1.1 KiB
|
|
-- Example: maximum in list
|
|
maximum :: (Ord a) -> [a] -> a
|
|
maximum [] = error "maximum of empty list"
|
|
maximum [x] = x
|
|
maximum (x:xs) = max x (maximum xs)
|
|
|
|
-- Another example, replicate
|
|
replicate (Num i, Ord i) => i -> a -> [a]
|
|
replicate n x
|
|
| n <= 0 = []
|
|
| otherwise = x:(replicate (n-1) x)
|
|
|
|
-- Now, take
|
|
take :: (Num i, Ord i) => i -> [a] -> [a]
|
|
take n _
|
|
| n <= 0 = [] -- if n is 0 or less, empty list
|
|
-- if guard is non-exhaustive, matching falls through to next pattern
|
|
take _ [] = []
|
|
take n (x:xs) = x:(take (n-1) xs)
|
|
|
|
reverse :: [a] -> [a]
|
|
reverse [] = []
|
|
reverse (x:xs) = (reverse xs) ++ [x]
|
|
|
|
zip :: [a] -> [b] -> [(a,b)]
|
|
zip _ [] = []
|
|
zip [] _ = []
|
|
zip (x:xs) (y:ys) = (x,y):(zip xs, ys)
|
|
|
|
elem :: (Eq a) => a -> [a] -> Bool
|
|
elem _ [] = False
|
|
elem a (x:xs)
|
|
| a == x = True
|
|
| otherwise = a `elem` xs
|
|
|
|
-- Double recursion!
|
|
quicksort :: (Ord a) => [a] -> [a]
|
|
quicksort [] = []
|
|
quicksort (x:xs) = let smallerSorted = quicksort [ a | a <- xs, a <= x ] in
|
|
let biggerSorted = quicksort [ a | a <- xs, a > x ] in
|
|
smallerSorted ++ [x] ++ biggerSorted
|