What is the significance of reverse polish notation?

Question

I teach computing to 18 year olds. After having reverse polish notation explained to them one asked why is it significant enough to be in the public exam. I explained the historical significance of 70s calculators but this failed to really address the issue. So are there and concurrent practical or theorhetical applications of RPN.

Answer 1

Yes, expressions are evaluated by creating an "expression tree", then by scanning the tree Leftsubtree-Rightsubtree - Node: [note: Postfix notation is RPN] -- no parentheses are needed.

So, Excel, Google, ... and compilers like Java, C, ..., and interpreters like RAPTOR, Flowgrarithm, etc. all use RPN. Many software applications also allow expressions that are evaluated the same way.

A = B + C

becomes the tree

............=

......../......\

......A.......+

............./....\

...........B.....C

Then:

ABC+= [in RPN]

Then, evaluated with a stack:

If value, push onto stack

If operator, pop two values from stack, perform operation, push result onto stack.

Note: A unary operator must get special treatment.