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In theoretical computer science, a Markov algorithm is a string rewriting system that uses grammar-like rules to operate on strings of symbols. Markov algorithms have been shown to be Turing-complete, which means that they are suitable as a general model of computation and can represent any mathematical expression from its simple notation.
The standard example here is the languages L k consisting of all strings over the alphabet {a,b} whose kth-from-last letter equals a. On the one hand, a regular expression describing L 4 is given by ( a ∣ b ) ∗ a ( a ∣ b ) ( a ∣ b ) ( a ∣ b ) {\displaystyle (a\mid b)^{*}a(a\mid b)(a\mid b)(a\mid b)} .
Start of string Before all other characters on page $ End of string After all other characters on page (or line if multiline option is active) \Z: End of string After all other characters on page \b: On a word boundary On a letter, number or underscore character \B: Not on a word boundary Not on a letter, number or underscore character
For example, a grammar for a context-free language is left-recursive if there exists a non-terminal symbol A that can be put through the production rules to produce a string with A as the leftmost symbol. [15] An example of recursive grammar is a clause within a sentence separated by two commas. [16]
For function that manipulate strings, modern object-oriented languages, like C# and Java have immutable strings and return a copy (in newly allocated dynamic memory), while others, like C manipulate the original string unless the programmer copies data to a new string.
The longest common substrings of a set of strings can be found by building a generalized suffix tree for the strings, and then finding the deepest internal nodes which have leaf nodes from all the strings in the subtree below it. The figure on the right is the suffix tree for the strings "ABAB", "BABA" and "ABBA", padded with unique string ...
long = CLng(string) float = CSng(string) double = CDbl(string) string = CStr(number) Visual Basic .NET (can use both VB syntax above and .NET methods shown right) integer = Integer.Parse (string) long = Long.Parse (string) float = Single.Parse (string) double = Double.Parse (string) string = number.ToString() Xojo: integer = Val(string) long ...
In cryptography, a substitution cipher is a method of encrypting in which units of plaintext are replaced with the ciphertext, in a defined manner, with the help of a key; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing ...