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Python: python.org: Python Software Foundation License: Python has two major implementations, the built in re and the regex library. Ruby: ruby-doc.org: GNU Library General Public License: 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 ...
"Regular expressions" […] are only marginally related to real regular expressions. Nevertheless, the term has grown with the capabilities of our pattern matching engines, so I'm not going to try to fight linguistic necessity here. I will, however, generally call them "regexes" (or "regexen", when I'm in an Anglo-Saxon mood). [19]
[1] [2] A predictive parser is a recursive descent parser that does not require backtracking . [ 3 ] Predictive parsing is possible only for the class of LL( k ) grammars, which are the context-free grammars for which there exists some positive integer k that allows a recursive descent parser to decide which production to use by examining only ...
Complex regular expressions can often be constructed in several different ways, all with the same outputs but with greatly varying efficiency. If AWB is taking a long time to generate results because of a regex rule: Try constructing the expression a different way. There are several online resources with guidance to creating efficient regex ...
Introduced in Python 2.2 as an optional feature and finalized in version 2.3, generators are Python's mechanism for lazy evaluation of a function that would otherwise return a space-prohibitive or computationally intensive list. This is an example to lazily generate the prime numbers:
the set of states Q = { q 0, q 1, q 2}, the input alphabet Σ = { a, b}, the transition function δ with δ(q 0,a)=q 0, δ(q 0,b)=q 1, δ(q 1,a)=q 2, δ(q 1,b)=q 1, δ(q 2,a)=q 1, and δ(q 2,b)=q 1, the start state q 0, and; set of accept states F = { q 1}. Kleene's algorithm computes the initial regular expressions as
In computer science, extended Backus–Naur form (EBNF) is a family of metasyntax notations, any of which can be used to express a context-free grammar.EBNF is used to make a formal description of a formal language such as a computer programming language.
Pages in category "Regular expressions" The following 12 pages are in this category, out of 12 total. This list may not reflect recent changes. ...