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Yacc (Yet Another Compiler-Compiler) is a computer program for the Unix operating system developed by Stephen C. Johnson.It is a lookahead left-to-right rightmost derivation (LALR) parser generator, generating a LALR parser (the part of a compiler that tries to make syntactic sense of the source code) based on a formal grammar, written in a notation similar to Backus–Naur form (BNF). [1]
[3] [4] It is frequently used as the lex implementation together with Berkeley Yacc parser generator on BSD-derived operating systems (as both lex and yacc are part of POSIX), [5] [6] [7] or together with GNU bison (a version of yacc) in *BSD ports [8] and in Linux distributions.
Lex is a computer program that generates lexical analyzers ("scanners" or "lexers"). [ 1 ] [ 2 ] It is commonly used with the yacc parser generator and is the standard lexical analyzer generator on many Unix and Unix-like systems.
Context-free languages are a category of languages (sometimes termed Chomsky Type 2) which can be matched by a sequence of replacement rules, each of which essentially maps each non-terminal element to a sequence of terminal elements and/or other nonterminal elements.
In the yacc and bison parser generators, the parser has an ad hoc mechanism to abandon the current statement, discard some parsed phrases and lookahead tokens surrounding the error, and resynchronize the parse at some reliable statement-level delimiter like semicolons or braces. This often works well for allowing the parser and compiler to look ...
Ox is an attribute grammar compiling system that augments Lex and Yacc specifications with definitions of synthesized and inherited attributes written in a combination of Ox and C/C++ syntax. From these specifications, Ox generates ordinary Lex and Yacc specifications that build and decorate an attributed parse tree.
The most established is lex, paired with the yacc parser generator, or rather some of their many reimplementations, like flex (often paired with GNU Bison). These generators are a form of domain-specific language, taking in a lexical specification – generally regular expressions with some markup – and emitting a lexer.
Bison has features not found in Yacc, so some projects can be truly said to "use" Bison, since Yacc would not suffice. The following list is of projects which are known to "use" Bison in the looser sense, that they use free software development tools and distribute code which is intended to be fed into Bison or a Bison-compatible package.