Formal languages

abstract computation model; mathematical model of computation that defines an abstract machine which manipulates symbols on a strip of tape according to a table of rules

sequence of characters that forms a search pattern

computer language for annotating documents

set of strings of symbols that may be constrained by rules that are specific to it; words whose letters are taken from an alphabet and are well-formed according to a specific set of rules

data type representing a finite sequence of encoded characters

containment hierarchy of classes of formal grammars

metasyntax notation for context-free grammars, developed by John Backus and Peter Naur for the ALGOL 60 report (1963); foundational to formal language specification in computer science

the simplest numeral system, a non-positional numeral system

structure of a formal language

any well-defined system of abstract thought based on the model of mathematics

formal grammar whose production rules can be applied to a nonterminal symbol regardless of its context

non-empty set of symbols or letters that make up strings in a formal language

unary operation on sets of strings, used in regular expressions for "zero or more repetitions"

thumb|upright=2| A spreadsheet's concatenate ("&") function is used to assemble a complex text string—in this example, XML code for an [[SVG "circle" element.]] In formal language theory and computer programming, string concatenation is the operation of joining character strings end-to-end. For example, the concatenation of "snow" and "ball" is "snowball". In certain formalizations of concatenation theory, also called string theory, string concatenation is a primitive notion.

diff is a shell command that compares the content of files and reports differences. The term diff is also used to identify the output of the command and is used as a verb for running the command. To diff files, one runs diff to create a diff.

formal language that can be expressed using a regular expression

family of metasyntax notations, any of which can be used to express a context-free grammar

form for context-free grammars

tree representation of the abstract syntactic structure of source code

formal language that is a member of the set of languages defined by context-free grammars

the unique string of length zero

sufficient evidence or a sufficient argument for the truth of a proposition

formal grammar in which components of production rules may be surrounded by a contextual symbols

formal grammar, that is right-regular or left-regular

recursive subset of the set of all possible finite sequences over the alphabet of the language

formal language that can be defined by a context-sensitive grammar (and equivalently by a noncontracting grammar). Context-sensitive is one of the four types of grammars in the Chomsky hierarchy

a formal language that can be output (enumerated) by an algorithm (mathematical logic, computability theory)

form for context-free grammars

assignment of meaning to the symbols of a formal language

type of pumping lemma

In mathematics, linguistics, computer science, and logic, rewriting covers a wide range of methods of replacing subterms of a formula with other terms. Such methods may be achieved by rewriting systems (also known as rewrite systems, rewrite engines, or reduction systems). In their most basic form, they consist of a set of objects, plus relations on how to transform those objects.

A bigram or digram is a sequence of two adjacent elements from a string of tokens, which are typically letters, syllables, or words. A bigram is an n-gram for n=2.

finite sequence of symbols from a given alphabet that is part of a formal language

Ambiguity in Grammar

theorem

categories of symbols in formal grammars

algorithm to find the longest increasing subsequence in an array of numbers

lemma giving a property shared by all context-free languages

establishment of a theorem using inference from the axioms

SCIgen is a paper generator that uses context-free grammar to randomly generate nonsense in the form of computer science research papers. Its original data source was a collection of computer science papers downloaded from CiteSeer. All elements of the papers are formed, including graphs, diagrams, and citations. Created by scientists at the Massachusetts Institute of Technology, its stated aim is "to maximize amusement, rather than coherence." Originally created in 2005 to expose the lack of scrutiny of submissions to conferences, the generator subsequently became used, primarily by Chinese a

rules used for constructing or transforming the symbols of a formal language

formal way to define attributes for the productions of a formal grammar, associating these attributes with values

generalization of the pumping lemma for context-free languages

Grammar model in linguistics

visual description of context-free grammar

formal language consisting of balanced strings of square brackets

thumb|"string" is a substring of "substring"

A metacharacter is a character that has a special meaning to a computer program, such as a shell interpreter or a regular expression (regex) engine. For instance, in XML, the character is interpreted not as ordinary text (in which it would be the less-than sign), but rather as a metacharacter signalling the beginning of an XML tag.

theory of computer science

context-free language that can be accepted by a deterministic pushdown automaton

language theory

formal grammar derived from a deterministic pushdown automaton

Abstract machine in computer science

metalanguage based on Backus–Naur Form (BNF)

approach to natural language semantics

basic element of strings in a formal language

formal language

in computer science, a rewrite rule specifying a substitution that can be recursively performed to generate new sequences

generalization of context-free grammars in that nonterminals are equipped with lists of flags, or index symbols