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The word boundary between such numeric portions and an alphabetic portions may include grey-space or not, but a phrase search turns off portioning, because it is an "exact phrase search", the words in the phrase matching only alphanumeric words delimited by grey-space.
A regular expression (shortened as regex or regexp), [1] sometimes referred to as rational expression, [2] [3] is a sequence of characters that specifies a match pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings , or for input validation .
Regular Expression Flavor Comparison – Detailed comparison of the most popular regular expression flavors; Regexp Syntax Summary; Online Regular Expression Testing – with support for Java, JavaScript, .Net, PHP, Python and Ruby; Implementing Regular Expressions – series of articles by Russ Cox, author of RE2; Regular Expression Engines
For example, a bare namespace returns the pages of the namespace. The query term1 term2 regexp relies heavily on the first two terms to reduce the search domain size. All terms in a query are indexed searches unless they are a regexp. Indexed terms run word-wise instantly, and a regexp runs character-wise slowly. Even the most basic use of a ...
Each regular expression is associated with a production rule in the lexical grammar of the programming language that evaluates the lexemes matching the regular expression. These tools may generate source code that can be compiled and executed or construct a state transition table for a finite-state machine (which is plugged into template code ...
Another approach is to indicate word boundaries using medial capitalization, called "camelCase", "PascalCase", and many other names, thus respectively rendering "two words" as "twoWords" or "TwoWords". This convention is commonly used in Pascal, Java, C#, and Visual Basic.
Add word boundaries (\b) to both ends of the regex unless you are matching errors in parts of words or multiple words. Do not expect rules to be applied in the order they appear. Write fast rules:
With online algorithms the pattern can be processed before searching but the text cannot. In other words, online techniques do searching without an index. Early algorithms for online approximate matching were suggested by Wagner and Fischer [3] and by Sellers. [2] Both algorithms are based on dynamic programming but solve different problems.