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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.
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 commercial version supported analysis of PHP and Java code. In order to identify security vulnerabilities that are based on second-order data flows or misplaced security mechanisms, it used abstract syntax trees, control-flow graphs, and context-sensitive taint analysis [7] It could automatically detect 200 different vulnerability types, code quality issues and misconfiguration weaknesses.
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 term closure is often used as a synonym for anonymous function, though strictly, an anonymous function is a function literal without a name, while a closure is an instance of a function, a value, whose non-local variables have been bound either to values or to storage locations (depending on the language; see the lexical environment section below).
Lexical analysis (including regular expressions and finite automata) Syntax analysis (including context-free grammars, LL parsers, bottom-up parsers, and LR parsers) Syntax-directed translation; Type checking (including type conversions and polymorphism) Run-time environment (including parameter passing, symbol tables and register allocation)
Here is a very simple program in re2c (example.re). It checks that all input arguments are hexadecimal numbers. The code for re2c is enclosed in comments /*!re2c ... */, all the rest is plain C code. See the official re2c website for more complex examples. [23]
A fundamental distinction in scope is what "part of a program" means. In languages with lexical scope (also called static scope), name resolution depends on the location in the source code and the lexical context (also called static context), which is defined by where the named variable or function is defined.