Actually, Haskell does let you write print statements for debugging. If we have the following function: foo :: Int -> Int foo x = x `div` 0 and we wa

Actually, Haskell does let you write print statements for debugging. If we have the following function: foo :: Int -> Int foo x = x `div` 0 and we want to add debugging, we can do: import Debug.Trace foo :: Int -> Int foo x | trace (show x) False = undefined | otherwise = x `div` 0 The above will print the value of x before throwing an error due to division by zero. You don't have to make foo return an IO Int or change any other aspect of your program.