Chapter 4, Problem 10RQ

Explanation of Solution

Parsing problem for a top-down parser:

The top down parser attempts for a left most derivation on a left sentential form to get the next sentential form.

• Suppose the left sentential form “xAa” has to be expanded to get the next form. We know that x is a string of terminals; A represents a non-terminal and α represents string containing both terminals and non-terminals.
• The parser attempts for an expansion from left hand side of “xAa” by replacing the left most non- terminal A.
• From the grammar rule the most appropriate rule with A on LHS is to be selected...