The question is somewhat unclear, but I try to answer the 'is it easy to create an algorithm which shows me what is the last computation'.
Think of rpn as a stack based method of calculation: so bc*a+
means push (the value of) b
on the stack, push c
on the stack, apply *
to the two topmost elements and push the result on the top of the stack. Then push a
on the stack and apply +
to the two topmost elements and push the result on the stack. So the last computation an rpn formula does is the right-most operator.
Logical sentences are exacty the same thing, just replace * with & and + with |.