Solve first lab

Exercises/exercise-1/Solution.hs

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+import Data.List (sort)
+
+--------------------
+-- Exercise 1
+--------------------
+flatSort :: [[Integer]] -> [Integer]
+flatSort x = concat (map (\y -> sort y) x)
+
+-- >>> flatSort [[1,2,3], [1,3,2]]
+-- [1,2,3,1,2,3]
+-- >>> flatSort [[1], [2]]
+-- [1,2]
+-- >>> flatSort [[1], [1,2], [1,2,3]]
+-- [1,1,2,1,2,3]
+
+--------------------
+-- Exercise 2
+--------------------
+xs :: [[Integer]]
+xs = [[1], [2, 1]]
+-- >>> (concat xs) /= (flatSort xs)
+-- True
+
+--------------------
+-- Exercise 3
+--------------------
+flatSort' xs =
+    case xs of
+        [] -> []
+        x:xs -> sort x ++ flatSort' xs
+
+--------------------
+-- Exercise 4
+--------------------
+initial :: String -> String -> Bool
+initial xs ys =
+    case xs of
+        [] -> True
+        x:xs -> (
+            case ys of
+                [] -> False
+                y:ys ->
+                    if x == y then
+                        initial xs ys
+                    else
+                        False)
+
+-- >>> initial "abc" "abcd"
+-- True
+-- >>> initial "abc" "xabcd"
+-- False
+
+--------------------
+-- Exercise 5
+--------------------
+substring :: String -> String -> Bool
+substring xs ys =
+    case ys of
+        [] -> False
+        _ -> initial xs ys || substring xs (tail ys)
+
+-- >>> substring "abc" "xadbcd"
+-- False
+-- >>> substring "abc" "xadbabccd"
+-- True
+-- >>> substring "abc" "ab"
+-- False