Grammars and Parsers: An Overview of Language Processing

This lecture covers the fundamentals of computer language processing, focusing on grammars and parsers. It begins with an introduction to formal grammars, defining them as sets of rewriting rules that consist of terminal and non-terminal symbols. The instructor explains the Chomsky hierarchy, detailing the different types of grammars: unrestricted, context-sensitive, context-free, and regular grammars, along with their properties and complexities. The lecture also discusses regular expressions and their role in describing regular languages. The concept of parse trees is introduced, illustrating how they represent the syntactic structure of recognized words. Common parsing challenges such as ambiguity and infinite recursion are addressed, along with strategies for disambiguation and left/right factoring. The lecture concludes with an overview of parsing algorithms, highlighting the differences between bottom-up and top-down approaches, and introduces parser combinators in Scala, demonstrating how parsers can be composed to handle complex language structures.