Notes on PDA Rules
•Interpretation of Apa ® wq: if the current state is p, current input symbol is a, and the topmost symbol on the pushdown is A, then M can read a, replace A with w and change state p to q.
• Note: if a = e, no symbol is read
•Strictly mathematically, R is a relation
  from G ´ Q ´ (S È {e}) to G* ´ Q
•Instead of (Apa, wq) Î R, however, we write Apa ® wq Î R
Mathematical note on rules:
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