Instruct: Classify a review as either positive or negative.
Query: Excellent reference for beginning or advanced users

I knew nothing about either lex or yacc when I picked up this book. However, John Levine clearly explains the basics, devoting separate tutorial chapters to both lex and yacc as well as two chapters for complete real-world examples (I was impressed with the chapter about parsing SQL). Despite the repeated nature of parts of the reference sections, I highly recommend the book to anybody else who needs to learn how lex and yacc work. Especially useful for identifying common problems. Includes documentation for nearly all of the functions lex and yacc define.