Context-free grammars

Abstract

In chapter 5 we use finite automata for text parsing. As noted, there are rather simple structures (e.g., nested comments) that cannot be parsed with finite automata. There is a more powerful formalism called context-free grammars that is often used when finite automata are not enough. In section 15.1 we define context-free grammars and consider a general polynomial parsing algorithm. However, this algorithm is not fast enough to be practical, and in the next two sections we consider faster (linear time) algorithms that can be used for some classes of context-free grammars, called recursive-descent parsing (section 15.2) and LL-parsing (section 15.3).