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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.
Regular expressions entered popular use from 1968 in two uses: pattern matching in a text editor [9] and lexical analysis in a compiler. [10] Among the first appearances of regular expressions in program form was when Ken Thompson built Kleene's notation into the editor QED as a means to match patterns in text files .
The star height problem in formal language theory is the question whether all regular languages can be expressed using regular expressions of limited star height, i.e. with a limited nesting depth of Kleene stars. Specifically, is a nesting depth of one always sufficient? If not, is there an algorithm to determine how many are required? The ...
In C and C++, 0 represents the null pointer. As with Boolean values, the C standard library includes a macro definition NULL whose use is encouraged. Other languages provide a specific null or nil value and when this is the case no alternative should be used. The typed pointer constant nullptr has been introduced with C++11.
A class diagram exemplifying the singleton pattern. In object-oriented programming, the singleton pattern is a software design pattern that restricts the instantiation of a class to a singular instance. It is one of the well-known "Gang of Four" design patterns, which describe how to solve recurring problems in object-oriented software. [1]
In C, array indexing is formally defined in terms of pointer arithmetic; that is, the language specification requires that array[i] be equivalent to *(array + i). [8] Thus in C, arrays can be thought of as pointers to consecutive areas of memory (with no gaps), [8] and the syntax for accessing arrays is identical for that which can be used to ...
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C and C++ do not have built-in support for glob patterns in the ISO-defined standard libraries, however on Unix-like systems C and C++ may include <glob.h> from the C POSIX library to use glob(). C++ itself does not have direct support for glob patterns, however they may be approximated using the <filesystem> and <regex> headers, using std ...