func (st *state) refQualifier() string {
	if len(st.str) > 0 {
		switch st.str[0] {
		case 'R':
			st.advance(1)
			return "&"
		case 'O':
			st.advance(1)
			return "&&"
		}
	}
	return ""
}
func (st *state) refQualifier() string {
	if len(st.str) > 0 {
		switch st.str[0] {
		case 'R':
			st.advance(1)
			return "&"
		case 'O':
			st.advance(1)
			return "&&"
		}
	}
	return ""
}
func ( st * state ) refQualifier ( ) string { if len ( st . str ) > 0 { switch st . str [ 0 ] { case 'R' : st . advance ( 1 ) return " " case 'O' : st . advance ( 1 ) return " " } } return " " }
// <ref-qualifier> ::= R
//                 ::= O
<ref - qualifier > :: = R :: = O