String operations: Difference between revisions

Revision as of 22:04, 11 January 2017

Revision as of 22:06, 11 January 2017

Line 1:

In [[computer science]], in the area of [[formal language theory]], frequent use is made of a variety of [[string functions]]; however, the notation used is different from that used onfor [[computer programming]], and some commonly used functions in the theoretical realm are rarely used when programming. This article defines some of these basic terms.

==Strings and languages==

Line 116:

==String projection==

If ''s'' is a string, and <math>\Sigma</math> is an alphabet, the '''string projection''' of ''s'' is the string that results by removing all letters whichthat are not in <math>\Sigma</math>. It is written as <math>\pi_\Sigma(s)\,</math>. It is formally defined by removal of letters from the right hand side:

:<math>\pi_\Sigma(s) = \begin{cases}