Idris style/semantics question: why does the last line of the first example in the article use parentheses[1] instead of another dollar sign[2]? [1] caesa

Idris style/semantics question: why does the last line of the first example in the article use parentheses[1] instead of another dollar sign[2]? [1] caesar_cipher : Int -> String -> String caesar_cipher shift input = let cipher = chr . (+ shift) . ord in pack $ map cipher (unpack input) [2] caesar_cipher : Int -> String -> String caesar_cipher shift input = let cipher = chr . (+ shift) . ord in pack $ map cipher $ unpack input To me the second one seems more readable. Are there semantic differences? Performance differences?