Overview of lex and yacc

I need to get an overview of how the entire process works. Lex and yacc were the first popular and efficient lexers and parsers generators, flex and bison were the first widespread opensource versions compatible with the original software. Each of these software has more than 30 years of history, which is an achievement in itself. I hope to use lex and yacc and encapsulate my utilities within a tiny subset of c and include. Write text parsers with yacc and lex ibm developer. Why you should not use flex, yacc and bison federico. Lex generates a deterministic finite automaton from the regular expressions in the source. Lex lex is a program generator that generates lexical analyzers, widely used on unix.

Sly is a 100% python implementation of the lex and yacc tools commonly used to write parsers and compilers. An overview of lex pllab, nthu,cs2403 programming languages 8 lex. The task of discovering the source structure again is decomposed into subtasks. Flex and bison are improved, modern versions of lex and yacc, standardly distributed with most. Yacc users will realize that the name yylex is what yacc expects its lexical analyzer to be named, so that the use of this name by lex simplifies interfacing. The asteroid to kill this dinosaur is still in orbit. Yacc uses grammar rules that allow it to analyze tokens from lex and create a syntax tree. It takes a sequence of tokens say, from lex and interprets them as series of statements.

Gnu has its own, enhanced, versions called flex and bison. Here we give a brief overview of their structure and use. It reads the input stream specifying the lexical analyzer and outputs source code implementing the lexical analyzer in the c programming language. Lex is a lexical analysis tool that can be used to identify specific text strings in a structured way from source text.

Flex and bison, clones for lex and yacc, can be obtained for free from gnu and cygwin. Ply is a 100% python implementation of the lex and yacc tools commonly used to write parsers and compilers. Find the hierarchical structure of the program yacc. Its power is roughly equivalent to regular expression matching. I assume you can program in c and understand data structures such as linkedlists and trees. Lex and yacc are tools used to generate lexical analyzers and parsers. Lex and yacc can generate program fragments that solve the first task. The overview describes the basic building blocks of a compiler and explains the interaction between lex and yacc. The automaton is interpreted, rather than compiled, in order to save space.

In fact, the additional features of flex and bison make them an irresistable choice. Ill keep referring to lex and yacc, but you can use flex and bison as dropin replacements in most cases. Overview of architecture, working, syntax of lexical analyzer and yacc and. Parsing is based on the same lalr1 algorithm used by many yacc tools. Yacc generates c code for a syntax analyzer, or parser.