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Has two implementations, with PCRE being the more efficient in speed, functions POSIX C POSIX.1 web publication: Licensed by the respective implementation Supports POSIX BRE and ERE syntax Python: python.org: Python Software Foundation License: Python has two major implementations, the built in re and the regex library. Ruby: ruby-doc.org
String functions are used in computer programming languages to manipulate a string or query information about a string (some do both). Most programming languages that have a string datatype will have some string functions although there may be other low-level ways within each language to handle strings directly. In object-oriented languages ...
Strings are passed to functions by passing a pointer to the first code unit. Since char * and wchar_t * are different types, the functions that process wide strings are different than the ones processing normal strings and have different names. String literals ("text" in the C source code) are converted to arrays during compilation. [2]
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 .
A parsing expression is a kind of pattern that each string may either match or not match.In case of a match, there is a unique prefix of the string (which may be the whole string, the empty string, or something in between) which has been consumed by the parsing expression; this prefix is what one would usually think of as having matched the expression.
In formal language theory and pattern matching (including regular expressions), the concatenation operation on strings is generalised to an operation on sets of strings as follows: For two sets of strings S 1 and S 2, the concatenation S 1 S 2 consists of all strings of the form vw where v is a string from S 1 and w is a string from S 2, or ...
When a language is given by a regular expression, the concept of derivatives leads to an algorithm for deciding whether a given word belongs to the regular expression. Given a finite alphabet A of symbols, [ 6 ] a generalized regular expression R denotes a possibly infinite set of finite-length strings over the alphabet A , called the language ...
The closeness of a match is measured in terms of the number of primitive operations necessary to convert the string into an exact match. This number is called the edit distance between the string and the pattern. The usual primitive operations are: [1] insertion: cot → coat; deletion: coat → cot