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module Main where

hello ∷ String
hello = "hello"

We define endline to be a function which adds a newline character to the end of a string. The ++ operator concatenates two lists; we can use it here because a string is a list of characters.

endline ∷ String → String
endline s = s ++ "\n"

Using endline, we can instead call the function putStr.

main ∷ IO ()
main = putStr (endline hello)

hello

Main.hs