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GNU Bison, commonly known as Bison, is a parser generator that is part of the GNU Project. Bison reads a specification in Bison syntax (described as "machine-readable BNF " [ 3 ] ), warns about any parsing ambiguities, and generates a parser that reads sequences of tokens and decides whether the sequence conforms to the syntax specified by the ...
A lookahead LR parser (LALR) generator is a software tool that reads a context-free grammar (CFG) ... for example GNU bison, a pun on the original Yacc/Yak.
Flex (fast lexical analyzer generator) is a free and open-source software alternative to lex. [2] It is a computer program that generates lexical analyzers (also known as "scanners" or "lexers").
The first algorithms for LALR parser generation were published in 1973. [4] In 1982, DeRemer and Tom Pennello published an algorithm that generated highly memory-efficient LALR parsers. [5] LALR parsers can be automatically generated from a grammar by an LALR parser generator such as Yacc or GNU Bison. The automatically generated code may be ...
However, parser generators for context-free grammars often support the ability for user-written code to introduce limited amounts of context-sensitivity. (For example, upon encountering a variable declaration, user-written code could save the name and type of the variable into an external data structure, so that these could be checked against ...
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]
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 ...
To recognize more complex languages, Lex is often used with parser generators such as Yacc or Bison. Parser generators use a formal grammar to parse an input stream. It is typically preferable to have a parser, one generated by Yacc for instance, accept a stream of tokens (a "token-stream") as input, rather than having to process a stream of ...