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In formal language theory, a context-free grammar ( CFG) is a formal grammar whose production rules can be applied to a nonterminal symbol regardless of its context. In particular, in a context-free grammar, each production rule is of the form. with a single nonterminal symbol, and a string of terminals and/or nonterminals ( can be empty).
The set of all context-free languages is identical to the set of languages accepted by pushdown automata, which makes these languages amenable to parsing.Further, for a given CFG, there is a direct way to produce a pushdown automaton for the grammar (and thereby the corresponding language), though going the other way (producing a grammar given an automaton) is not as direct.
To convert a grammar to Chomsky normal form, a sequence of simple transformations is applied in a certain order; this is described in most textbooks on automata theory. [ 4 ] : 87–94 [ 5 ] [ 6 ] [ 7 ] The presentation here follows Hopcroft, Ullman (1979), but is adapted to use the transformation names from Lange, Leiß (2009).
English grammar is the set of structural rules of the English language.This includes the structure of words, phrases, clauses, sentences, and whole texts.. This article describes a generalized, present-day Standard English – a form of speech and writing used in public discourse, including broadcasting, education, entertainment, government, and news, over a range of registers, from formal to ...
Just Words. If you love Scrabble, you'll love the wonderful word game fun of Just Words. Play Just Words free online! By Masque Publishing. Advertisement. Advertisement. Feedback. Help. Join AOL.
Backus–Naur form. In computer science, Backus–Naur form ( / ˌbækəs ˈnaʊər /) (BNF or Backus normal form) is a notation used to describe the syntax of programming languages or other formal languages. It was developed by John Backus and Peter Naur. BNF can be described as a metasyntax notation for context-free grammars.
MPEG-4 Part 14, or MP4, is a digital multimedia container format most commonly used to store video and audio, but it can also be used to store other data such as subtitles and still images. Like most modern container formats, it allows streaming over the Internet. The only filename extension for MPEG-4 Part 14 files as defined by the ...
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