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Instead of doing a basic indexed search on keywords, you can perform a regex search, which bypasses the index.A regex search scans the text of each page on Wikipedia in real time, character by character, to find pages that match a specific sequence or pattern of characters.
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 ...
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.
In theoretical computer science and formal language theory, a regular language (also called a rational language) [1] [2] is a formal language that can be defined by a regular expression, in the strict sense in theoretical computer science (as opposed to many modern regular expression engines, which are augmented with features that allow the recognition of non-regular languages).
RE2 is a software library which implements a regular expression engine. It uses finite-state machines, in contrast to most other regular expression libraries. RE2 supports a C++ interface. RE2 was implemented by Google and Google uses RE2 for Google products. [3]
where A, B, S ∈ N are non-terminal symbols, a ∈ Σ is a terminal symbol, and ε denotes the empty string, i.e. the string of length 0. S is called the start symbol. In a left-regular grammar, (also called left-linear grammar), all rules obey the forms A → a; A → Ba; A → ε
While PCRE originally aimed at feature-equivalence with Perl, the two implementations are not fully equivalent. During the PCRE 7.x and Perl 5.9.x phase, the two projects coordinated development, with features being ported between them in both directions. [5] In 2015, a fork of PCRE was released with a revised programming interface (API).
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