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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 .
Ruby 1.8, Ruby 1.9, and Ruby 2.0 and later versions use different engines; Ruby 1.9 integrates Oniguruma, Ruby 2.0 and later integrate Onigmo, a fork from Oniguruma. Rust: docs.rs: MIT License: The primary regex crate does not allow look-around expressions. There is an Oniguruma binding called onig that does. SAP ABAP: SAP.com: Proprietary: Tcl ...
In computer science, Thompson's construction algorithm, also called the McNaughton–Yamada–Thompson algorithm, [1] is a method of transforming a regular expression into an equivalent nondeterministic finite automaton (NFA). [2] This NFA can be used to match strings against the regular expression.
Perl Compatible Regular Expressions (PCRE) is a library written in C, which implements a regular expression engine, inspired by the capabilities of the Perl programming language. Philip Hazel started writing PCRE in summer 1997. [ 3 ]
The sequence operator e 1 e 2 first invokes e 1, and if e 1 succeeds, subsequently invokes e 2 on the remainder of the input string left unconsumed by e 1, and returns the result. If either e 1 or e 2 fails, then the sequence expression e 1 e 2 fails (consuming no input). The choice operator e 1 / e 2 first invokes e 1, and if e 1 succeeds ...
Perl is particularly noted for its regular expression use, [21] and many other languages and applications implement Perl compatible regular expressions. Some languages such as Perl and Ruby support string interpolation , which permits arbitrary expressions to be evaluated and included in string literals.
The digit the farthest to the right (which is multiplied by 1) is the check digit, chosen to make the sum correct. It may need to have the value 10, which is represented as the letter X. For example, take the ISBN 0-201-53082-1: The sum of products is 0×10 + 2×9 + 0×8 + 1×7 + 5×6 + 3×5 + 0×4 + 8×3 + 2×2 + 1×1 = 99 ≡ 0 (mod 11). So ...
Since 7 October 2024, Python 3.13 is the latest stable release, and it and, for few more months, 3.12 are the only releases with active support including for bug fixes (as opposed to just for security) and Python 3.9, [55] is the oldest supported version of Python (albeit in the 'security support' phase), due to Python 3.8 reaching end-of-life.