Shoutbox

Yes... but it's a less natural notation...
Implementation that use PostFix notation (RPN) are stack based... operands are popped from a stack, and calculation results are pushed back onto it. Although this concept may seem obscure at first, RPN has the advantage of being extremely easy for a computer to analyze due to it being a regular grammar.

I prefer to use Infix notation because it's easier to write the algebric expression. I'm not sure that everybody are familiar with Postfix ...


One classic exercise in computer science is to write a parser for algebraic expressions, that is, a program that takes an input string like


(3 + 5) * (-4 + (2 - 9))


and calculates the result of this expression. In fact, what you do to compute that expression is to convert it into an internal representation, and then evaluate that representation.

You can represent the expression given above by a linked list:

where each node of the list either contains an operator or a number. Once the arithmetic expression is given in list form, evaluating it is easy and can be done in a straightforward, object oriented way...