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# Topic: Regular language

###### In the News (Thu 21 Jun 18)

 PlanetMath: regular language A regular language (also known as a regular set or a regular event) is the set of strings generated by a regular grammar. Note that since the set of regular languages is a subset of context-free languages, any deterministic or non-deterministic finite automaton can be simulated by a pushdown automaton. This is version 11 of regular language, born on 2002-02-23, modified 2007-08-19. www.planetmath.org /encyclopedia/RegularLanguage.html   (309 words)

 Syntax and Semantics of Regular Expressions - Xerox XRCE Enclosing a regular expression in round parentheses (as opposed to square brackets) represents a union with the empty-string language. The opposite of the null language is the universal language. " in the sense of "the language denoted by the regular expression www.xrce.xerox.com /competencies/content-analysis/fsCompiler/fssyntax.html   (2518 words)

 Regular expression - Wikipedia, the free encyclopedia A regular expression (abbreviated as regexp, regex, or regxp, with plural forms regexps, regexes, or regexen) is a string that describes or matches a set of strings, according to certain syntax rules. Regular expressions are used by many text editors and utilities to search and manipulate bodies of text based on certain patterns. Regular expressions correspond to the type 3 grammars of the Chomsky hierarchy and may be used to describe a regular language. en.wikipedia.org /wiki/Regular_expression   (3269 words)

 Regular language - Wikipedia, the free encyclopedia If a language is not regular, it requires a machine with at least O(log log n) space to recognize (where n is the input size). To prove that a language such as this is not regular, one uses the Myhill-Nerode theorem or the pumping lemma. The language L is regular if and only if the number of equivalence classes of ~ is finite; if this is the case, this number is equal to the number of states of the minimal deterministic finite automaton accepting L. en.wikipedia.org /wiki/Regular_language   (583 words)

 CMSC 451 Lecture 9, Intersection of languages, closure Regular languages are closed under operations: concatenation, union, intersection, complementation, difference, reversal, Kleene star, substitution, homomorphism and any finite combination of these operations. We have seen that regular languages are closed under union because the "+" is regular expressions yields a union operator for regular languages. Regular set properties: One way to show that an operation on two regular languages produces a regular language is to construct a machine that performs the operation. www.csee.umbc.edu /~squire/cs451_l9.html   (782 words)

 Encyclopedia: Regular language The regular grammars describe exactly all regular languages and are in that sense equivalent with finite state automata and regular expressions. Moreover, the right regular grammars by themselves are also equivalent to the regular languages, as are the left regular grammers. Regular grammars, which use either left-regular or right-regular rules but not both, can only express a smaller set of languages, called the regular languages. www.nationmaster.com /encyclopedia/Regular-language   (595 words)

 Formal Language Definitions L(G) is the notation for a language defined by a grammar G. The grammar G recognizes a certain set of strings, thus a language. The building blocks of regular languages are symbols, concatenation of symbols to make strings (words), set union of strings and Kleene closure (denoted as *, also called the Kleene star, it should be typed as a superscript but this is plain text.) Informally, we use a syntax for regular expressions. The language class P is the set of languages for which there exists a deterministic Turing machine that accepts each language in a number of transitions bounded by a fixed polynomial in the length of the input string. www.cs.umbc.edu /help/theory/lang_def.shtml   (1263 words)

 Regular languages * (negation) of a regular language is a regular language. A regular expression is a compact notation for representing a particular regular language, using concatenation, union and unbounded repetition. The language generated by RG is the set L consisting of strings that have terminated derivations. dingo.sbs.arizona.edu /~langendoen/LING501/LING501regular.htm   (757 words)

 [No title] phi (the empty-set symbol) is a regular language expression and the corresponding regular expression is phi. {lambda} is a regular language, and the corresponding regular expression is lambda. For each a in E, {a} is a regular language, and a is the corresponding regular expression. www.ecst.csuchico.edu /~kent/Cs256/student256/chap3notes   (1141 words)

 [No title] phi is a regular expression denoting language {} 2. For all a in Sigma, a is a regular expression denoting {a} 4. Regular expressions are "language generators", they provide a mechanism to list elements of a language. ranger.uta.edu /~cook/tcs/l5.html   (1095 words)

 Syntax of Regular Expressions (Finite-State Calculus) In general, the concatenation of two regular languages consists of strings that extend each string of the first language with all the strings of the second language. Enclosing a regular expression in round parentheses (as opposed to square brackets) represents a union with the empty-string language. " in the sense of "the language denoted by the regular expression www.cis.upenn.edu /~cis639/docs/fssyntax.html   (2451 words)

 [No title]   (Site not responding. Last check: 2007-10-30) These formal languages are characterized by grammars which are essentially a set of rewrite rules for generating strings belonging to a language as we see later. In asddition two of the formal languages, regular and context-free languages, are quite useful for modeling systems used in practice such as co9mputer network communication protocols, lexical analyzers and parser for compilers for programming languages. Then we study regular languages, the simplest of the four formal languages, together with regular expressions which are a method of representing regular languages. www.cs.odu.edu /~toida/nerzic/390teched/language/intro.html   (525 words)

 Cover Pages: Regular Language Description for XML (RELAX) RELAX (REgular LAnguage description for XML) "is a specification for describing XML-based languages. RELAX (REgular LAnguage description for XML) is a namespace-aware specification for describing XML-based languages which borrows rich datatypes from XML Schema Part 2; the RELAX grammar can be written as an XML document. Although the XMLNews-Story markup language has been superseded by the News Industry Text Format, I've chosen it because it's simple, quite widely used, looks a great deal like HTML, and its RELAX specification will use most of the features we want to focus on. xml.coverpages.org /relax.html   (2827 words)

 Regular Language Regular expressions and regular grammars can be thought of as “generators” of strings in a language and automata can be thought of as “acceptors” of strings in a language.  The set of all languages that these constructs are capable of working with is known as the “regular” languages. Invoke this option to create a regular expression in memory which represents the same regular language as the automaton currently in memory.  The algorithm RLM uses to accomplish this is taken from [1], but a slight optimization has been made. Invoke this option to create a regular grammar in memory which represents the same regular language as the automaton currently in memory.  The algorithm RLM uses to accomplish this is taken from [1]. www.theese.com /rlm/rlm.html   (4175 words)

 AWK Language Programming - Regular Expressions A regular expression, or regexp, is a way of describing a set of strings. A regular expression can be used as a pattern by enclosing it in slashes. Regular expressions can also be used in matching expressions. www.math.utah.edu /docs/info/gawk_5.html   (2909 words)

 Formal Language Definitions   (Site not responding. Last check: 2007-10-30) L(M) is the notation for a language defined by a machine M. The machine M accepts a certain set of strings, thus defines a language. L(G) is the notation for a language defined by a grammar G. The grammar G recognizes a certain set of strings, thus defines a language. L = L1 â© L2 The complement of a language is a language. cs.wwc.edu /~aabyan/CC2001/AL/lang_def.html   (1520 words)

 Regular language   (Site not responding. Last check: 2007-10-30) The results of the union, intersection and set-difference operations when applied to regular languages is itself a regularlanguage; the complement of every regular language is a regular language as well. Concatenating two regular languages (in the sense of concatenating every string from the firstlanguage with every string from the second one) also yields a regular language. The rightquotient and the leftquotient of a regular language by an arbitrary language is also regular. www.therfcc.org /regular-language-34498.html   (503 words)

 [No title] This true because every description of a regular language is of finite length, so there is a countably infinite number of such descriptions. Showing That a Language is Regular Techniques for showing that a language L is regular: Show that L has a finite number of elements. Using Closure Properties Once we have some languages that we can prove are not regular, such as anbn, we can use the closure properties of regular languages to show that other languages are also not regular. www.cs.utexas.edu /users/cline/ear/Slides/Regular/RegularSlides5.doc   (1994 words)

 [No title]   (Site not responding. Last check: 2007-10-30) Regular Expressions, Languages, and Grammars A class of languages called “regular languages” is of interest to us. There are 3 ways to describe a regular language: regular expression the set containing the elements in the language regular grammar Regular Expressions We can construct regular expressions from primitive constituents by repeatedly applying recursive rules: Let A be a given alphabet. These are primitive regular expressions if w1 and w2 are regular expressions, then w1(w2, w1 (w2, w1*, and (w1) are regular expressions a string is a regular expression if and only if it can be derived from the primitive regular expressions by a finite number of applications of the rules in (2). www.utdallas.edu /~kcooper/teaching/2305/FSA/FSA.doc   (1170 words)

 Cellular Automata as Models of Complexity (1984) The words in a regular language correspond to the possible paths through a finite graph representing a finite state machine. in the smallest graph corresponding to a particular set of configurations may be defined as the `regular language complexity' of the set. Formal languages are recognized or generated by idealized computers with a `central processing unit' containing a fixed finite number of internal states, together with a `memory'. www.stephenwolfram.com /publications/articles/ca/84-cellular/9/text.html   (597 words)

 Closure Proof Template The language A' is the concatenation of two languages: A and B, where language B = {"1"}. B is a regular language [this is pretty obvious but if want to be very rigorous you could draw a little DFA that recognizes B]. Since A' is the concatenation of two regular languages, and we know regular languages are closed under concatenation, then A' is also regular. www-cse.ucsd.edu /users/clbailey/ClosureProofTemplate.htm   (1413 words)

 Regular Expression HOWTO Since regular expressions are used to operate on strings, we'll begin with the most common task: matching characters. Regular expressions are often used to dissect strings by writing a RE divided into several subgroups which match different components of interest. Regular expressions are a powerful tool for some applications, but in some ways their behaviour isn't intuitive and at times they don't behave the way you may expect them to. www.amk.ca /python/howto/regex   (6489 words)

 Cover Pages: Regular Language Description for XML (RELAX) RELAX (REgular LAnguage description for XML) "is a specification for describing XML-based languages. RELAX (REgular LAnguage description for XML) is a namespace-aware specification for describing XML-based languages which borrows rich datatypes from XML Schema Part 2; the RELAX grammar can be written as an XML document. Although the XMLNews-Story markup language has been superseded by the News Industry Text Format, I've chosen it because it's simple, quite widely used, looks a great deal like HTML, and its RELAX specification will use most of the features we want to focus on. www.oasis-open.org /cover/relax.html   (2827 words)

 English Language School-Regular Programs   (Site not responding. Last check: 2007-10-30) The Primary Mission of the intensive English program of the English Language Institute is to prepare international students for study at the graduate or undergraduate level in institutions of higher learning in the USA. The ELI also provides intensive language instruction to persons already trained in their professions and others who wish to improve their level of English proficiency and cultural awareness. For these reasons, it is the policy of the English Language Institute that English be used in all communications among students as well as students and employees, and we assume that, by applying for admission, you accept our rule on the use of English. www.eli.ufl.edu /firsttime/regular.htm   (776 words)

 Talk:Regular language The word regular is used because these expressions are built up using very distinct limited and regulated syntax rules. I think one could argue that context-free languages are also built according to limited syntax rules. I'm pretty sure the word "regular" was chosen without much thinking; it's one of those meaningless terms, like "normal", that are used all over the place. www.termsdefined.net /ta/talk:regular-language.html   (357 words)

 [No title] Theorem 1.13 47 The class of regular languages is closed under the concatenation operation. Theorem 1.22 59 The class of regular languages is closed under the union operation. Theorem 1.23 60 The class of regular languages is closed under the concatenation operation. www.geneffects.com /briarskin/860/thms.txt   (1936 words)

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