{ @empty-string describe-error := "string is empty"

  (s: String) indent: (n: Integer) :=
    s lines (map: { l | $  (repeat: n) .. l }) (join: "\n")

  (s: String) word-wrap: (length: Integer) :=
    s lines
      (map: { l | (l take-while: @space?) .. (wrap-line: l to: length) })
      unlines

  wrap-line: l to: length :=
    { words = l words

      line-length = 0

      ok-words =
        words take-while:
          { w |
            line-length = line-length + 1 + w length
            line-length < length
          } in-context

      [ ok-words unwords
        words (drop: ok-words length) unwords word-wrap: length
      ] unlines strip-end
    } call
} call