code: func NewRegexpTokenizer(pattern string, gaps, discard bool) *RegexpTokenizer {
  	rTok := RegexpTokenizer{
  		regex: regexp.MustCompile(pattern), gaps: gaps, discard: discard}
  	return &rTok
  }
docs: // NewRegexpTokenizer is a RegexpTokenizer constructor that takes three
  // arguments: a pattern to base the tokenizer on, a boolean value indicating
  // whether or not to look for separators between tokens, and boolean value
  // indicating whether or not to discard empty tokens.