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Syntax Definition Formalism
The Syntax Definition Formalism (SDF) is a metasyntax used to define context-free grammars: that is, a formal way to describe formal languages. It can express the entire range of context-free grammars. Its current version is SDF3. A parser and parser generator for SDF specifications are provided as part of the free ASF+SDF Meta Environment. These operate using the SGLR ( Scannerless GLR parser). An SDF parser outputs parse trees or, in the case of ambiguities, parse forests. Overview Features of SDF: * Supports the entire range of context-free languages * Allows modular syntax definitions (grammars can import subgrammars) which enables reuse * Supports annotations Examples The following example defines a simple Boolean expression syntax in SDF2: module basic/Booleans exports sorts Boolean context-free start-symbols Boolean context-free syntax "true" -> Boolean "false" -> Boolean lhs:Boolean ", " rhs:Boolean -> Boole ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metasyntax
In logic and computer science, a metasyntax describes the allowable structure and composition of phrases and sentences of a metalanguage, which is used to describe either a natural language or a computer programming language.Sellink, Alex, and Chris Verhoef.Development, assessment, and reengineering of language descriptions" Software Maintenance and Reengineering, 2000. Proceedings of the Fourth European. IEEE, 2000. Some of the widely used formal metalanguages for computer languages are Backus–Naur form (BNF), extended Backus–Naur form (EBNF), Wirth syntax notation (WSN), and augmented Backus–Naur form (ABNF). These metalanguages have their own metasyntax each composed of terminal symbols, nonterminal symbols, and ''metasymbols''. A terminal symbol, such as a word or a token, is a stand-alone structure in a language being defined. A nonterminal symbol represents a syntactic category, which defines one or more valid phrasal or sentence structure consisted of an n-element subs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Context-free Grammar
In formal language theory, a context-free grammar (CFG) is a formal grammar whose production rules are of the form :A\ \to\ \alpha with A a ''single'' nonterminal symbol, and \alpha a string of terminals and/or nonterminals (\alpha can be empty). A formal grammar is "context-free" if its production rules can be applied regardless of the context of a nonterminal. No matter which symbols surround it, the single nonterminal on the left hand side can always be replaced by the right hand side. This is what distinguishes it from a context-sensitive grammar. A formal grammar is essentially a set of production rules that describe all possible strings in a given formal language. Production rules are simple replacements. For example, the first rule in the picture, :\langle\text\rangle \to \langle\text\rangle = \langle\text\rangle ; replaces \langle\text\rangle with \langle\text\rangle = \langle\text\rangle ;. There can be multiple replacement rules for a given nonterminal symbol. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parser
Parsing, syntax analysis, or syntactic analysis is the process of analyzing a string of symbols, either in natural language, computer languages or data structures, conforming to the rules of a formal grammar. The term ''parsing'' comes from Latin ''pars'' (''orationis''), meaning part (of speech). The term has slightly different meanings in different branches of linguistics and computer science. Traditional sentence parsing is often performed as a method of understanding the exact meaning of a sentence or word, sometimes with the aid of devices such as sentence diagrams. It usually emphasizes the importance of grammatical divisions such as subject and predicate. Within computational linguistics the term is used to refer to the formal analysis by a computer of a sentence or other string of words into its constituents, resulting in a parse tree showing their syntactic relation to each other, which may also contain semantic and other information (p-values). Some parsing algor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parser Generator
In computer science, a compiler-compiler or compiler generator is a programming tool that creates a parser, interpreter, or compiler from some form of formal description of a programming language and machine. The most common type of compiler-compiler is more precisely called a parser generator. It only handles syntactic analysis. The input of a parser generator is a grammar file, typically written in Backus–Naur form (BNF) or extended Backus–Naur form (EBNF) that defines the syntax of a target programming language. The output is the source code of a parser for the programming language. The output of the (compiled) parser source code is a parser. It may be either standalone or embedded. This parser takes as an input the source code of the target programming language source and performs some action or outputs an abstract syntax tree (AST). Parser generators do not handle the semantics of the AST, or the generation of machine code for the target machine."A Syntax Directed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ASF+SDF Meta Environment
ASF may refer to: Arts and entertainment * Alabama Shakespeare Festival, a drama festival * ''Asimov's Science Fiction'', a U.S.-based English-language science fiction magazine containing SF stories Science and technology Biological * African swine fever virus (ASFV), the causative agent of African swine fever (ASF) * Altered Schaedler flora, a standardized consortium of gastrointestinal microbial species * Serine/arginine-rich splicing factor 1, a protein also known as alternative splicing factor 1 (ASF) Computing * Advanced Synchronization Facility, a proposed extension to the x86 instruction set architecture * Advanced Systems Format (formerly "Advanced Streaming Format", .asf), a Microsoft streaming format * Alert Standard Format, a protocol for remote management and control of systems in OS-absent environments * Antispam, Anti Spam Filtering, software and hardware protection layers used to fight email spam * Apache Software Foundation, an umbrella non-profit organ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scannerless Parsing
In computer science, scannerless parsing (also called lexerless parsing) performs tokenization (breaking a stream of characters into words) and parsing (arranging the words into phrases) in a single step, rather than breaking it up into a pipeline of a lexer followed by a parser, executing concurrently. A language grammar is scannerless if it uses a single formalism to express both the lexical (word level) and phrase level structure of the language. Dividing processing into a lexer followed by a parser is more modular; scannerless parsing is primarily used when a clear lexer–parser distinction is unneeded or unwanted. Examples of when this is appropriate include TeX, most wiki grammars, makefiles, simple application-specific scripting languages, and Raku. Advantages * Only one metalanguage is needed * Non-regular lexical structure is handled easily * "Token classification" is unneeded which removes the need for design accommodations such as "the lexer hack" and language r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GLR Parser
A GLR parser (GLR standing for "Generalized LR", where L stands for "left-to-right" and R stands for "rightmost (derivation)") is an extension of an LR parser algorithm to handle non-deterministic and ambiguous grammars. The theoretical foundation was provided in a 1974 paper by Bernard Lang (along with other general Context-Free parsers such as GLL). It describes a systematic way to produce such algorithms, and provides uniform results regarding correctness proofs, complexity with respect to grammar classes, and optimization techniques. The first actual implementation of GLR was described in a 1984 paper by Masaru Tomita, it has also been referred to as a "parallel parser". Tomita presented five stages in his original work, though in practice it is the second stage that is recognized as the GLR parser. Though the algorithm has evolved since its original forms, the principles have remained intact. As shown by an earlier publication, Lang was primarily interested in more easily use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parse Tree
A parse tree or parsing tree or derivation tree or concrete syntax tree is an ordered, rooted tree that represents the syntactic structure of a string according to some context-free grammar. The term ''parse tree'' itself is used primarily in computational linguistics; in theoretical syntax, the term ''syntax tree'' is more common. Concrete syntax trees reflect the syntax of the input language, making them distinct from the abstract syntax trees used in computer programming. Unlike Reed-Kellogg sentence diagrams used for teaching grammar, parse trees do not use distinct symbol shapes for different types of constituents. Parse trees are usually constructed based on either the constituency relation of constituency grammars (phrase structure grammars) or the dependency relation of dependency grammars. Parse trees may be generated for sentences in natural languages (see natural language processing), as well as during processing of computer languages, such as programming languages. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ambiguous Grammar
In computer science, an ambiguous grammar is a context-free grammar for which there exists a string that can have more than one leftmost derivation or parse tree, while an unambiguous grammar is a context-free grammar for which every valid string has a unique leftmost derivation or parse tree. Many languages admit both ambiguous and unambiguous grammars, while some languages admit only ambiguous grammars. Any non-empty language admits an ambiguous grammar by taking an unambiguous grammar and introducing a duplicate rule or synonym (the only language without ambiguous grammars is the empty language). A language that only admits ambiguous grammars is called an inherently ambiguous language, and there are inherently ambiguous context-free languages. Deterministic context-free grammars are always unambiguous, and are an important subclass of unambiguous grammars; there are non-deterministic unambiguous grammars, however. For computer programming languages, the reference grammar is ofte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RascalMPL
Rascal is an experimental domain specific language for metaprogramming, such as static code analysis, program transformation, program generation and implementation of domain specific languages. It is a general meta language in the sense that it does not have a bias for any particular software language. It includes primitives from relational calculus and term rewriting. Its syntax and semantics are based on procedural (imperative) and functional programming. See also * ASF+SDF * Stratego/XT * DMS Software Reengineering Toolkit * ANTLR * Source-to-source compiler A source-to-source translator, source-to-source compiler (S2S compiler), transcompiler, or transpiler is a type of translator that takes the source code of a program written in a programming language as its input and produces an equivalent sou ... References {{reflist, refs= {{Citation , first1=Paul , title=2009 Ninth IEEE International Working Conference on Source Code Analysis and Manipulation , last1=Klint , ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
