**Are you an EPFL student looking for a semester project?**

Work with us on data science and visualisation projects, and deploy your project as an app on top of Graph Search.

Concept# String operations

Summary

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 for computer programming, and some commonly used functions in the theoretical realm are rarely used when programming. This article defines some of these basic terms.
A string is a finite sequence of characters.
The empty string is denoted by .
The concatenation of two string and is denoted by , or shorter by .
Concatenating with the empty string makes no difference: .
Concatenation of strings is associative: .
For example, .
A language is a finite or infinite set of strings.
Besides the usual set operations like union, intersection etc., concatenation can be applied to languages:
if both and are languages, their concatenation is defined as the set of concatenations of any string from and any string from , formally .
Again, the concatenation dot is often omitted for brevity.
The language consisting of just the empty string is to be distinguished from the empty language .
Concatenating any language with the former doesn't make any change: ,
while concatenating with the latter always yields the empty language: .
Concatenation of languages is associative: .
For example, abbreviating , the set of all three-digit decimal numbers is obtained as . The set of all decimal numbers of arbitrary length is an example for an infinite language.
The alphabet of a string is the set of all of the characters that occur in a particular string. If s is a string, its alphabet is denoted by
The alphabet of a language is the set of all characters that occur in any string of , formally:
For example, the set is the alphabet of the string ,
and the above is the alphabet of the above language as well as of the language of all decimal numbers.
Let L be a language, and let Σ be its alphabet. A string substitution or simply a substitution is a mapping f that maps characters in Σ to languages (possibly in a different alphabet).

Official source

This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Related MOOCs (2)

Related publications (15)

Related courses (23)

Related concepts (16)

Related lectures (87)

Introduction to Programming in C++

Ce cours initie à la programmation en utilisant le langage C++. Il ne présuppose pas de connaissance préalable. Les aspects plus avancés (programmation orientée objet) sont donnés dans un cours suivan

Introduction to Programming in Java

Ce cours initie à la programmation en utilisant le langage Java. Il ne présuppose pas de connaissance préalable. Les aspects plus avancés (programmation orientée objet) sont donnés dans un cours suiva

Semiautomaton

In mathematics and theoretical computer science, a semiautomaton is a deterministic finite automaton having inputs but no output. It consists of a set Q of states, a set Σ called the input alphabet, and a function T: Q × Σ → Q called the transition function. Associated with any semiautomaton is a monoid called the characteristic monoid, input monoid, transition monoid or transition system of the semiautomaton, which acts on the set of states Q.

Combinatorics on words

Combinatorics on words is a fairly new field of mathematics, branching from combinatorics, which focuses on the study of words and formal languages. The subject looks at letters or symbols, and the sequences they form. Combinatorics on words affects various areas of mathematical study, including algebra and computer science. There have been a wide range of contributions to the field. Some of the first work was on square-free words by Axel Thue in the early 1900s. He and colleagues observed patterns within words and tried to explain them.

Substring

In formal language theory and computer science, a substring is a contiguous sequence of characters within a string. For instance, "the best of" is a substring of "It was the best of times". In contrast, "Itwastimes" is a subsequence of "It was the best of times", but not a substring. Prefixes and suffixes are special cases of substrings. A prefix of a string is a substring of that occurs at the beginning of ; likewise, a suffix of a string is a substring that occurs at the end of .

ME-213: Programmation pour ingénieur

Mettre en pratique les bases de la programmation vues au semestre précédent. Développer un logiciel structuré. Méthode de debug d'un logiciel. Introduction à la programmation scientifique. Introductio

CS-108: Practice of object-oriented programming

Les étudiants perfectionnent leurs connaissances en Java et les mettent en pratique en réalisant un projet de taille conséquente. Ils apprennent à utiliser et à mettre en œuvre les principaux types de

CS-320: Computer language processing

We teach the fundamental aspects of analyzing and interpreting computer languages, including the techniques to build compilers. You will build a working compiler from an elegant functional language in

LabVIEW Programming Essentials

Explores LabVIEW essentials, troubleshooting common issues, managing cache, and data visualization techniques.

Engineering Projects Overview

Provides an overview of engineering projects, troubleshooting tips, and practical demonstrations on signal processing and Arduino integration.

Programming for Engineers: LabVIEW Essentials

Introduces LabVIEW essentials for engineers, covering loops, structures, dataflow, error handling, clusters, strings, and graph customization.

This thesis focuses on two selected learning problems: 1) statistical inference on graphs models, and, 2) gradient descent on neural networks, with the common objective of defining and analysing the measures that characterize the fundamental limits.In the ...

String matching is the problem of deciding whether a given n-bit string contains a given k-bit pattern. We study the complexity of this problem in three settings. - Communication complexity. For small k, we provide near-optimal upper and lower bounds on th ...

, , ,

Self-similar structures occur naturally and have been employed to engineer exotic physical properties. We show that acoustic modes of a fractal-like system of tensioned strings can display increased mechanical quality factors due to the enhancement of diss ...