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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").
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.
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.
The system uses a DFA for lexical analysis and the LALR algorithm for parsing. Both of these algorithms are state machines that use tables to determine actions. GOLD is designed around the principle of logically separating the process of generating the LALR and DFA parse tables from the actual implementation of the parsing algorithms themselves.
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.
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 ...
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.
Ragel is a finite-state machine compiler and a parser generator. Initially Ragel supported output for C, C++ and Assembly source code, [4] later expanded to support several other languages including Objective-C, D, Go, Ruby, and Java. [5] Additional language support is also in development. [6]