if (idx==-1) idx = i;
else return Sequence.create(p.nonTerminal, p.elements, p.drops, false);
if (idx != -1) return Sequence.create(els, idx);
if (idx==-1) idx = i;
else return Sequence.create(p.nonTerminal, p.elements, p.drops, false);
if (idx != -1) return Sequence.create(els, idx);