PEG.js and empty sequences

Question

I'm trying to implement the TPTP grammar in PEG. It contains a rule for an empty sequence, which is used in many other rules, and PEG is rejecting this. A Google search finds https://github.com/pegjs/pegjs/commit/df154daafb9c6c952351493af02d3a55e0b05c59#commitcomment-10667420 which seems to be saying PEG by design does not allow empty sequence rules, which would make it unsuitable for implementing grammars such as TPTP which contain such. Do I understand this correctly, or am I missing something?

Answer 1

I believe it is still possible to do so, as explained in the posted link; instead of matching with nothing, you can match with "", and then return whatever you want to return :

Empty
    = "" {return null;}