DEVELOPER_NOTES

the top of the pushdown store:
  the top of the pushdown store is on the left meaning that transition function (r, xyz) \in (q, 0, abc) will pop symbol a first than symbol b and then symbol c, push symbol z then symbol y and finally symbol x. The typical representation is a vector of symbols so for the pop part forward iterators begin and end should be used and for the push part reversed iterators rbegin and rend should be used. This is very much similar to grammars where context free grammars generating a string or a sentential from a rules say A -> aBb| c product a^ncb^n. First b is pushed then B and finally a.