Haskell - Usage of higher order functions (2) P31745

Implement the following functions using higher-order functions (and other predefined functions) of Haskell without using recursion.

1. Implement a function flatten :: [[Int]] -> [Int] that flattens a list of lists of integers in a list of integers.

2. Implement a function myLength :: String -> Int that returns the length of a string.

3. Implement a function myReverse :: [Int] -> [Int] that reverses a list of integers.

4. Implement a function countIn :: [[Int]] -> Int -> [Int] that, given a list of sublists $\ell$ and an element $x$, returns the list that tells who many times $x$ appears in each sublist of $\ell$.

5. Implement a function firstWord :: String -> String that, given a string with blanks and alphabetic characters, returns its first word.

Scoring

Each function scores 20 points.