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What is the relationship between regular expressions and context-free grammars?
Regular expressions and context-free grammars are both formal languages used in computer science to describe patterns in strings. Regular expressions are simpler and more limited in their expressive power, while context-free grammars are more complex and can describe a wider range of patterns. Regular expressions can be converted into context-free grammars, but not all context-free grammars can be represented by regular expressions.
What is the complement of a regular language and how does it relate to the concept of regular expressions?
The complement of a regular language is the set of all strings that are not in the original language. In terms of regular expressions, the complement of a regular language can be represented by negating the regular expression that defines the original language.
How do you use regular expression in web mining?
Regular expressions can be used to find patterns within data. Beyond that the subject of Regular expressions gets extremely complicated very fast, I suggest you purchase a book on the subject and read it... twice.. http://www.amazon.com/Mastering-Regular-Expressions-Jeffrey-Friedl/dp/0596528124/ref=sr_1_1?ie=UTF8&qid=1345423498&sr=8-1&keywords=regular+expressions
How can I simplify regular expressions using a regex simplifier tool?
To simplify regular expressions using a regex simplifier tool, you can input your complex regular expression into the tool, and it will analyze and simplify it for you. This can help make your regular expression more concise and easier to understand.
What is the time complexity of regular expressions (regex) operations?
The time complexity of regular expressions (regex) operations is typically O(n), where n is the length of the input string being processed.
How can you use the OR condition in PHP validation in regular expressions?
You use instead of OR
Can you use Perl regular expressions in PHP?
Yes, by using the preg_match() function
What is relation between regular languages finite automaton and regular grammars?
finite automaton is the graphical representation of language and regular grammar is the representation of language in expressions
What is the difference between transition graph and generalized transition graph?
A generalized transition graph is a transition graph whose edges are labeled with regular expressions; otherwise it is same as the usual transition graph. source: Introduction to Formal Languages and Automata by Peter Linz , Regular expressions and regular languages, page 81
Is there is any function or class in Java to check inputed string is valid char sequence and no numbers or any special char are there?
You should probably use regular expressions. For example, the following will check that the String s has only English (Latin) characters in it:boolean hasOnlyLatin = s.matches("^[a-zA-Z]*$");Learning to use regular expressions is scary at first, but worthwhile. See the related links for some information about regular expressions in Java.
What is the use of regular expression?
Regular expressions are useful in the production of syntax-highlightingsystems, data-validation, and many other tasks.While regular expressions would be useful on search-engine-computingsuch as google, processing them across the entire database could consume excessive computer resources depending on the complexity and design of the regex. Although in many cases system administrators
What is better Finite Automata or Regular Expression?
Finite Automata and Regular Expressions are equivalent. Any language that can be represented with a regular expression can be accepted by some finite automaton, and any language accepted by some finite automaton can be represented by a regular expression.
