• Couldn't match expected type ‘[Letter]’
                  with actual type ‘[Letter] -> [(a, [Letter])]’
    • Probable cause: ‘p’ is applied to too few arguments
      In the first argument of ‘f’, namely ‘p’
      In the first argument of ‘return’, namely ‘(f p)’
      In the expression: return (f p)
    • Relevant bindings include
        p :: [Letter] -> [(a, [Letter])] (bound at src/Main.hs:49:28)
        f :: [Letter] -> [(a -> b, [Letter])] (bound at src/Main.hs:49:13)
        (<*>) :: Parser (a -> b) -> Parser a -> Parser b
          (bound at src/Main.hs:49:16)
   |
49 |     (Parser f) <*> (Parser p) = return (f p)
   |                                           ^