excerpt (ActionView::Helpers::TextHelper)

    # File lib/action_view/helpers/text_helper.rb, line 113
            def excerpt(text, phrase, radius = 100, excerpt_string = "...")
              if text && phrase
                phrase = Regexp.escape(phrase)

                if found_pos = text.chars =~ /(#{phrase})/i
                  start_pos = [ found_pos - radius, 0 ].max
                  end_pos   = [ [ found_pos + phrase.chars.length + radius - 1, 0].max, text.chars.length ].min

                  prefix  = start_pos > 0 ? excerpt_string : ""
                  postfix = end_pos < text.chars.length - 1 ? excerpt_string : ""

                  prefix + text.chars[start_pos..end_pos].strip + postfix
                else
                  nil
                end
              end
            end