What is ANTLR used for?

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.

Is ANTLR top down or bottom up?

Both types of parser generators exist (for example yacc and bison are bottom-up and ANTLR and JavaCC are top-down).

How do I learn ANTLR?

What you need to do to get a parse tree:

1. define a lexer and parser grammar.
2. invoke ANTLR: it will generate a lexer and a parser in your target language (e.g., Java, Python, C#, JavaScript)
3. use the generated lexer and parser: you invoke them passing the code to recognize and they return to you a parse tree.

What does ANTLR generate?

ANTLR can generate lexers, parsers, tree parsers, and combined lexer-parsers. Other than lexers and parsers, ANTLR can be used to generate tree parsers. These are recognizers that process abstract syntax trees, which can be automatically generated by parsers.

How does ANTLR parser work?

ANTLR is code generator. It takes so called grammar file as input and generates two classes: lexer and parser. The stream of tokes is passed to parser which do all necessary work. It is the parser who builds abstract syntax tree, interprets the code or translate it into some other form.

What is the output of ANTLR?

The output of the Antlr Parser is to produce a source tree from the parse tree. It also has the option to add ASTM script to produce a semantic tree from the parse tree. From the semantic tree, the source tree is produced as output.

Is ANTLR recursive descent?

ANTLR generates top-down, recursive-descent, mostly non- speculating parsers, which means it supports source-level de- bugging, produces high-quality error messages, and allows programmers to embed arbitrary actions.

Is ANTLR context-free?

In fact, there are context-free grammars that you can “specify” with ANTLR that it cannot process correctly, which is true of most parser generators. (For ANTLR, this includes grammars with indirect left recursion, ambiguity, arbitrary lookahead, etc.)

What is ANTLR fragment?

ANTLR Lexer rules in v4 Fragments Fragments are reusable parts of lexer rules which cannot match on their own – they need to be referenced from a lexer rule.

What type of parser is ANTLR?

ANTLR is a powerful parser generator that you can use to read, process, execute, or translate structured text or binary files. It’s widely used in academia and industry to build all sorts of languages, tools, and frameworks. Twitter search uses ANTLR for query parsing, with over 2 billion queries a day.

What is visitor in ANTLR?

ANTLR Visitors The difference between listener and visitor mechanisms is listener methods are called by the ANTLR-provided walker object, whereas visitor methods must walk their children with explicit visit calls. In visitor we have the ability to tree walking while in listener you are only reacting to the tree walker.

Is predictive parser free from backtracking?

A predictive parser is a recursive descent parser that does not require backtracking. Any context-free grammar can be transformed into an equivalent grammar that has no left recursion, but removal of left recursion does not always yield an LL(k) grammar.