code: func (e *edit) ReplaceN(r []Replacer, n int) error {
  	return e.genReplace(r, n)
  }
docs: // ReplaceN replaces regular expressions mathed in r. The count determines the
  // number to match:
  //   n > 0: at most n matches
  //   n == 0: the result is none
  //   n < 0: all matches