Haskell — Vel Tech Exam 2018

1. Write a function df :: Int -> Int that returns the double factorial of a natural number. The double factorial of $n$ is denoted $n!!$ and is $n(n-2)(n-4)\dots$.

2. Write a function sumd :: Int -> Int that returns the sum of the digits of a natural number.

3. Write a function dup :: [Int] -> [Int] that duplicates each element in a list.

4. Write a function pal :: String -> Bool that tells if a string is a palindrome, ie, if it is equal to its reverse.

5. Write a function apply2 :: (a -> a) -> a -> a that applies a function twice to some parameter.

Problem information

Author: Jordi Petit

Generation: 2026-02-03T17:01:44.383Z

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