Chapter 4, Problem 14E

Explanation of Solution

Building parse tree automatically during a top-down or bottom- up parse:

• The automatic parse tree generation is explained in Figure 2.19.
• Based on the Figure 2.19, revise that for top-down parser.
• The following program demonstrates building of automatic parse tree.

    $\begin{array}{l}\text{terminal = 1 }\text{. }\text{. number\_of\_terminals}\\ \text{non\_terminal = number\_of\_terminals + 1 }\text{. }\text{. number\_of\_symbols}\\ \text{symbol = 1 }\text{. }\text{. number\_of\_symbols}\\ \text{production = 1 }\text{. }\text{. number\_of\_productions}\end{array}$

    $\begin{array}{l}\text{node = record}\\ \text{parent : symbol}\\ \text{children : list of node}\\ \text{parse\_tab : array [non\_terminal, terminal] of record}\end{array}$

    $\begin{array}{l}\text{action : (predict, error)}\\ \text{prod : production}\\ \text{prod\_tab : array [production] of list of symbol}\\ \text{--these}\text{two}\text{tables}\text{are}\text{created}\text{by}\text{a}\text{parser}\text{generator}\end{array}$

    $\begin{array}{l}\text{parse\_stack : stack of node}\\ \text{root : node := new node(start\_symbol, null)}\\ \text{parse\_stack}\end{array}$