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In theoretical computer science and formal language theory, a regular language is said to be star-free if it can be described by a regular expression constructed from the letters of the alphabet, the empty word, the empty set symbol, all boolean operators – including complementation – and concatenation but no Kleene star. [1]
In a refined Chomsky hierarchy, the class of pattern languages is a proper superclass and subclass of the singleton [note 2] and the indexed languages, respectively, but incomparable to the language classes in between; due to the latter, the pattern language class is not explicitly shown in the table below.
This has led to a nomenclature where the term regular expression has different meanings in formal language theory and pattern matching. For this reason, some people have taken to using the term regex, regexp, or simply pattern to describe the latter. Larry Wall, author of the Perl programming language, writes in an essay about the design of Raku:
The language C* adds to C a "domain" data type and a selection statement for parallel execution in domains. For the CM-2 models the C* compiler translated the code into serial C, calling PARIS (Parallel Instruction Set) functions, and passed the resulting code to the front end computer's native compiler.
The knowledge that northern and southern star patterns differed goes back to Classical writers, who describe, for example, the African circumnavigation expedition commissioned by Egyptian Pharaoh Necho II in c. 600 BC and those of Hanno the Navigator in c. 500 BC.
Roles are part of the sister language Raku. [30] With the acceptance of the Corinna OOP Proposal [31] Perl will have roles native to the language as part of a modern OOP system. PHP: Since version 5.4, [32] [33] PHP allows users to specify templates that provide the ability to "inherit" from more than one (trait-)class, as a pseudo multiple ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 25 February 2025. General-purpose programming language "C programming language" redirects here. For the book, see The C Programming Language. Not to be confused with C++ or C#. C Logotype used on the cover of the first edition of The C Programming Language Paradigm Multi-paradigm: imperative (procedural ...
A basic example of string searching is when the pattern and the searched text are arrays of elements of an alphabet Σ. Σ may be a human language alphabet, for example, the letters A through Z and other applications may use a binary alphabet (Σ = {0,1}) or a DNA alphabet (Σ = {A,C,G,T}) in bioinformatics.