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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 RE/flex lexical analyzer generator accepts an extended syntax of Flex lexer specifications as input. The RE/flex specification syntax is more expressive than the traditional Flex lexer specification syntax and may include indentation anchors, word boundaries, lazy quantifiers (non-greedy, lazy repeats), and new actions such as wstr() to ...
A rule-based program, performing lexical tokenization, is called tokenizer, [1] or scanner, although scanner is also a term for the first stage of a lexer. A lexer forms the first phase of a compiler frontend in processing. Analysis generally occurs in one pass.
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. An equivalent tool is specified as part of the POSIX standard. [3]
It is the lexer generator adopted by projects such as PHP, [4] SpamAssassin, [5] Ninja build system [6] and others. Together with the Lemon parser generator, re2c is used in BRL-CAD . [ 7 ] This combination is also used with STEPcode, an implementation of ISO 10303 standard.
JavaCC (Java Compiler Compiler) is an open-source parser generator and lexical analyzer generator written in the Java programming language. [ 2 ] JavaCC is similar to yacc in that it generates a parser from a formal grammar written in EBNF notation.
The first edition (1986) is informally called the "red dragon book" to distinguish it from the second edition [5] and from Aho & Ullman's 1977 Principles of Compiler Design sometimes known as the "green dragon book". [5] Topics covered in the first edition include: Compiler structure; Lexical analysis (including regular expressions and finite ...
One delicate issue with LR parser generators is the resolution of conflicts (shift/reduce and reduce/reduce conflicts). With many LR parser generators, resolving conflicts requires the analysis of the parser automaton, which demands some expertise from the user.