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An abstract syntax tree (AST) is a data structure used in computer science to represent the structure of a program or code snippet. It is a tree representation of the abstract syntactic structure of text (often source code) written in a formal language.
The parsing stage itself can be divided into two parts: the parse tree, or "concrete syntax tree", which is determined by the grammar, but is generally far too detailed for practical use, and the abstract syntax tree (AST), which simplifies this into a usable form. The AST and contextual analysis steps can be considered a form of semantic ...
The following is a simple context-free grammar which can describe a language made up of multiplication and addition of integers. Expr → Expr + Term Expr → Term Term → Term * Factor Term → Factor Factor → "(" Expr ")" Factor → integer. The following attribute grammar can be used to calculate the result of an expression written in the ...
Tree-sitter parsers have been written for these languages and many others. [11] GitHub uses Tree-sitter to support in-browser symbolic code navigation in Git repositories. [12] Tree-sitter uses a GLR parser, a type of LR parser. [13] [14] [12] Tree-sitter was originally developed by GitHub for use in the Atom text editor, where it was first ...
Many modern approaches to dependency tree parsing use transition-based parsing (the base form of this is sometimes called arc-standard) as formulated by Joakim Nivre in 2003, [19] which extends on shift-reduce parsing by keeping a running stack of tokens, and deciding from three operations for the next token encountered:
Grammatical Framework (GF) is a programming language for writing grammars of natural languages. GF is capable of parsing and generating texts in several languages simultaneously while working from a language-independent representation of meaning. Grammars written in GF can be compiled into a platform independent format and then used from ...
In computer-based language recognition, ANTLR (pronounced antler), or ANother Tool for Language Recognition, is a parser generator that uses a LL(*) algorithm for parsing. ANTLR is the successor to the Purdue Compiler Construction Tool Set ( PCCTS ), first developed in 1989, and is under active development.
The end result is then a shared-forest of possible parse trees, where common trees parts are factored between the various parses. This shared forest can conveniently be read as an ambiguous grammar generating only the sentence parsed, but with the same ambiguity as the original grammar, and the same parse trees up to a very simple renaming of ...