yacc

The computer program yacc is a parser generator developed by Stephen C. Johnson at AT&T for the Unix operating system. The name is an acronym for "Yet Another Compiler Compiler." It generates a parser (the part of a compiler that tries to make syntactic sense of the source code) based on an analytic grammar written in a notation similar to BNF. Yacc generates the code for the parser in the C programming language.

Yacc used to be available as the default parser generator on most Unix systems. It has since been supplanted as the default by more recent, largely compatible, programs such as Berkeley Yacc, GNU bison, MKS yacc and Abraxas pcyacc. An updated version of the original AT&T version is included as part of Sun's OpenSolaris project. Each offers slight improvements and additional features over the original Yacc, but the concept has remained the same. Yacc has also been rewritten for other languages, including Ratfor, EFL, ML, Ada, Java, and Limbo.

The parser generated by Yacc requires a lexical analyzer. Lexical analyzer generators, such as Lex or Flex are widely available. The IEEE POSIX P1003.2 standard defines the functionality and requirements for both Lex and Yacc.

Some versions of AT&T Yacc have become open source. For example, source code (for different implementations) is available with the standard distributions of Plan 9 and OpenSolaris.

See also

• LALR parser: The underlying parsing algorithm in Yacc.
• Bison: The GNU version of Yacc.
• Lex (and Flex lexical analyser), the token parser commonly used in conjunction with yacc (and Bison).
• BNF, is a metasyntax used to express context-free grammars: that is, a formal way to describe formal languages.

References

• Stephen C. Johnson. YACC: Yet another compiler-compiler. Unix Programmer's Manual Vol 2b, 1979.

External links

• Tutorial a lex/yacc/compiler tutorial by Arnab Chakrobarty.
• Yaxx yacc variant written to avoid dependencies on any particular programming language.
• Berkeley Yacc: yacc variant written to avoid dependencies on any particular C compiler.
• Essence, an LR(1) parser generator for Scheme
• ML-Yacc a yacc version for the Standard ML language.
• CL-Yacc, a LALR(1)parser generator for Common Lisp.
• Yecc a yacc version for Erlang.
• Happy a yacc-like parser generator for Haskell.
• PLY a SLR and LALR(1) parser generator for Python
• Eyapp an extension of yacc for Perl
• A Compact Guide To lex & yacc
• TPYACC, a Turbo Pascal or Delphi version of YACC
• The Gardens Point Parser Generator (GPPG), an implementation for C#