scan

# File lib/erb.rb, line 410
        def scan
          stag_reg = /(.*?)(<%%|<%=|<%#|<%|\n|\z)/
          etag_reg = /(.*?)(%%>|%>|\n|\z)/
          scanner = StringScanner.new(@src)
          while ! scanner.eos?
            scanner.scan(@stag ? etag_reg : stag_reg)
            text = scanner[1]
            elem = scanner[2]
            yield(text) unless text.empty?
            yield(elem) unless elem.empty?
          end
        end