Pic graham

O ld Stack =    = {Ą .., P_f3, P_t2, Ą_j}

P_k right of linę P_f2P_k__l => pop P_{k l} off stack P_k right of linę P_t3P_t2 => pop P_t2 off stack P_k left of linę P_tĄP_t3 => push P_k onto stack New Stack =    = {P₀,...,Ę₃,P_k}