Other libraries are better.
Haskellの文字列型同士の変換が欲しい場合はconvertibleかstring-conversionsを使うと良い感じです - ncaq
simple and easy haskell string transform wrapper.
toString
toByteStringStrict
toByteStringLazy
toShortByteString
toTextStrict
toTextLazy
It wrapper expect that ByteString
encode is utf-8.