Reverse Polish notation
= Reverse Polish notation
{wiki}
= Postfix notation
{synonym}
Place each operator after its operands. A binary application encodes its first subtree, then its second subtree, then the operator, a <postorder traversal>. A <stack machine> evaluates the tokens in one pass, popping the right operand before the left one. Reversing a <Polish notation> token list also reverses operand order: prefix subtraction `- a b` would become `b a -` rather than the required `a b -`.