Why Did/Does HP Use RPN?
In the years that followed, computer scientists realized that RPN or postfix notation was very efficient for computer math. As a postfix expression is scanned from left to right, operands are simply placed into a last-in, first-out (LIFO) stack and operators may be immediately applied to the operands at the bottom of the stack. By contrast, expressions with parentheses and precedence (infix notation) require that operators be delayed until some later point. Thus, the compilers on on almost all modern computers converted statements to RPN for execution. (In fact, some computer manufacturers designed their computers around postfix notation.)” (from the link above, on http://www.hpmuseum.org/rpn.htm) • Preorder traversal represents the expressions in Polish notation (which is what LISP uses (LISP stands for “God’s Computer Language”)). Like postorder, preorder doesn’t require parentheses (provided the operators are binary). Exercise #5, p. 374/381 (and write the expression in prefix an
