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For example, insource:/[a-z]{2}/ matches exactly 2 lowercase letters in a row. insource:/[a-z]{2,4}/ matches any string of 2, 3, or 4 lowercase letters. insource:/[a-z]{2,}/ matches any string of 2 or more lowercase letters. [ ] introduce a character class, which matches a single instance of any of the characters in the class.
Regular expressions are used in search engines, in search and replace dialogs of word processors and text editors, in text processing utilities such as sed and AWK, and in lexical analysis. Regular expressions are supported in many programming languages. Library implementations are often called an "engine", [4] [5] and many of these are ...
Regular expressions (or regex) are a common and very versatile programming technique for manipulating strings. On Wikipedia you can use a limited version of regex called a Lua pattern to select and modify bits of text from a string. The pattern is a piece of code describing what you are looking for in the string.
The literal starts with r followed by any number of #, followed by one ". Further " contained in the literal are considered part of the literal, unless followed by at least as many # as used after the opening r. As such, a string literal opened with r#" cannot have "# in its content.
find wildcard expressions and regular expressions. A search matches what you see rendered on the screen and in a print preview. The raw "source" wikitext is searchable by employing the insource parameter. For these two kinds of searches a word is any string of consecutive letters and numbers matching a whole word or phrase.
Regex searches are likely to time out unless you further limit the search in some way, such as by including another parameter or a search term outside of the insource component of the search string. (For example, X* intitle:/X/ to restrict the search to initial position.) For more details, see mw:Help:CirrusSearch#Regular expression searches.
Say the search box is given two words. The search starts with two index lookups, and the two results are combined with a logical AND. But before they are displayed as search results, they must all be assigned a final score before the top twenty (listed on the first page) can be displayed, and they must be formatted with snippets and highlighting.
Let c be the number of concatenation of the regular expression E and let s be the number of symbols apart from parentheses — that is, |, *, a and ε. Then, the number of states of A is 2s − c (linear in the size of E). The number of transitions leaving any state is at most two.