What is ANTLR used for?

ANTLR (ANother Tool for Language Recognition) is a tool for processing structured text. It does this by giving us access to language processing primitives like lexers, grammars, and parsers as well as the runtime to process text against them. It’s often used to build tools and frameworks.

What is Lexer grammar?

A lexer (often called a scanner) breaks up an input stream of characters into vocabulary symbols for a parser, which applies a grammatical structure to that symbol stream.

What is ANTLR 3?

ANTLR 3 is one such tool. ANTLR stands for ANother Tool for Language Recognition. It provides a Java-based framework for generating recognizers, parsers, and translators from a grammar. Terrence Parr, a professor of computer science at the University of San Francisco, created ANTLR and continues to develop it actively.

What is grammar in parsing?

In computer science, a parsing expression grammar (PEG), is a type of analytic formal grammar, i.e. it describes a formal language in terms of a set of rules for recognizing strings in the language.

What is ANTLR v4?

ANTLR v4 is a powerful tool used for building new programming languages and processing/translating structured text or binary files. ANTLR uses a grammar you create to generate a parser which can build and traverse a parse tree (or abstract syntax tree, AST).

What are tokens and lexemes?

Token: A token is a group of characters having collective meaning: typically a word or punctuation mark, separated by a lexical analyzer and passed to a parser. A lexeme is an actual character sequence forming a specific instance of a token, such as num.

How do you implement a lexer?

A lexer for a language can be implemented in two ways:

  1. By using a new code from scratch.
  2. By using a special source code generator tool for custom lexers like GNU Flex or Lex.

What is antlr3 runtime?

The runtime library for parsers generated by the C# target of ANTLR 3. This package supports projects targeting . NET 2.0 or newer, and built using Visual Studio 2008 or newer.

How do you parse a sentence example?

To parse this sentence, we first classify each word by its part of speech: the (article), man (noun), opened (verb), the (article), door (noun). The sentence has only one verb (opened); we can then identify the subject and object of that verb.

How do you write a parser in grammar?

Writing a parser

  1. Write many functions and keep them small. In every function, do one thing and do it well.
  2. Do not try to use regexps for parsing. They don’t work.
  3. Don’t attempt to guess. When unsure how to parse something, throw an error and make sure the message contains the error location (line/column).