Regular expressions are patterns used to match strings in programs like sed, awk, grep, and others. They descend from finite automata theory and are used for tasks like searching text files, lexical analysis of programming languages, and early web search engines. In Linux systems, regular expressions are used by commands like sed, grep, and vi. Sed can perform editing operations on lines that match regular expression addresses.
n this presentation, Manoj K. has talked about “Regular Expression”. Here he has explained how Regular Expressions are used. He has covered all of the codes and what they are used for. The goal is to teach you how to use regular expressions once and for all.
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n this presentation, Manoj K. has talked about “Regular Expression”. Here he has explained how Regular Expressions are used. He has covered all of the codes and what they are used for. The goal is to teach you how to use regular expressions once and for all.
----------------------------------------------------------
Get Socialistic
Our website: http://valuebound.com/
LinkedIn: http://bit.ly/2eKgdux
Facebook: https://www.facebook.com/valuebound/
Twitter: https://twitter.com/valuebound
This slide is prepared By these following Students of Dept. of CSE JnU, Dhaka. Thanks To: Nusrat Jahan, Arifatun Nesa, Fatema Akter, Maleka Khatun, Tamanna Tabassum.
Regular Expressions (RegEx) is a very powerful search pattern language used to filter data from vast database. Here is an in-depth tutorial about regular expressions and their usage in Search Engine Optimization (SEO) and for managing vast amount of data in popular tools like Notepad++, Excel Sheet etc...
Push Down Automata (PDA) | TOC (Theory of Computation) | NPDA | DPDAAshish Duggal
Push Down Automata (PDA) is part of TOC (Theory of Computation)
From this presentation you will get all the information related to PDA also it will help you to easily understand this topic. There is also one example.
This PPT is very helpful for Computer science and Computer Engineer
(B.C.A., M.C.A., B.TECH. , M.TECH.)
Design and Analysis of Algorithm help to design the algorithms for solving different types of problems in Computer Science. It also helps to design and analyze the logic of how the program will work before developing the actual code for a program.
This slide is prepared By these following Students of Dept. of CSE JnU, Dhaka. Thanks To: Nusrat Jahan, Arifatun Nesa, Fatema Akter, Maleka Khatun, Tamanna Tabassum.
Regular Expressions (RegEx) is a very powerful search pattern language used to filter data from vast database. Here is an in-depth tutorial about regular expressions and their usage in Search Engine Optimization (SEO) and for managing vast amount of data in popular tools like Notepad++, Excel Sheet etc...
Push Down Automata (PDA) | TOC (Theory of Computation) | NPDA | DPDAAshish Duggal
Push Down Automata (PDA) is part of TOC (Theory of Computation)
From this presentation you will get all the information related to PDA also it will help you to easily understand this topic. There is also one example.
This PPT is very helpful for Computer science and Computer Engineer
(B.C.A., M.C.A., B.TECH. , M.TECH.)
Design and Analysis of Algorithm help to design the algorithms for solving different types of problems in Computer Science. It also helps to design and analyze the logic of how the program will work before developing the actual code for a program.
Regular Expressions, most often known as “RegEx” is one of the most popular and widely accepted technology used for parsing the specific data contents from large text.
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Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
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Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
2. •A regular expression (regex) describes a pattern to match multiple input strings.
•Regular expressions descend from a fundamental concept in Computer Science
called finite automata theory
•Regular expressions are endemic to Unix
•Some utilities/programs that use them:
– vi, ed, sed, and emacs
– awk, tcl, perl and Python
– grep, egrep, fgrep
– compilers
•The simplest regular expression is a string of literal characters to match.
•The string matches the regular expression if it contains the substring.
What is a Regular Expression?
INTRODUCTION
9. In linux operating System:
Regular expressions are used by several different
Unix commands, including ed, sed, awk,
grep, and, to a more limited extent, vi.
Sed also understands something called addresses.
Addresses are either particular locations in a file or
a range where a particular editing command
should be applied. When Sed encounters no
addresses, it performs its operations on every line
in the file.
10. Sed stands for stream editor is a stream oriented
editor which was created exclusively for executing
scripts. Thus all the input you feed into it passes
through and goes to STDOUT and it does not change
the input file.
Oracles implementation is the extension of the
POSIX
(Portable Operating system for UNIX)
11. Editing Commands
COMMANDS ACTION
Insert
i, a
I, A
o, O
Insert text before, after cursor
Insert text before beginning, after end of line
Open new line for text below, above cursor
12. Editing Commands
COMMANDS ACTION
Change
r
cw
c
Replace character
Change word
Change current line
cmotion
C
R
s
Change text between the cursor and the target
of motion
Change to end of line
Type over (overwrite) characters
Substitute: delete character and insert new text
S Substitute: delete current line and insert new text
13. Application in Search Engine
One use of regular expressions that used to be very
common was in web search engines.
Archie, one of the first search engines, used regular
expressions exclusively to search through a database
of filenames on servers.
Regular expressions were chosen for these early
search engines because of both their power and easy
implementation.
14. In the case of a search engine, the strings input to
the regular expression would be either whole web
pages or a pre-computed index of a web page that
holds only the most important information from
that web page.
A query such as regular expression could be
translated into the following regular expression.
(Σ∗regularΣ∗expressionΣ∗ )∗∪
(Σ∗expressionΣ∗regularΣ∗ )∗ Σ, then, of course,
would be the set of all characters in the character
encoding used with this search engine.
15. Regular expressions are not used anymore in the
large web search engines because with the growth of
the web it became impossibly slow to use regular
expressions. They are however still used in many
smaller search engines such as a find/replace tool in
a text editor or tools such as grep.
17. Regular Expressions in Lexical Analysis
To perform lexical analysis, two components are
required: a scanner and a tokenizer.
The purpose of tokenization is to categorize the
lexemes found in a string to sort them by meaning.
The process can be considered a sub-task of parsing
input.
18. For example, the C programming language could
contain tokens such as numbers, string constants,
characters, identifiers (variable names), keywords, or
operators.
We can simply define a set of regular expressions,
each matching the valid set of lexemes that belong to
this token type. This is the process of scanning.
19. This process can be quite complex and may require
more than one pass to complete.
Another option is to use a process known as
backtracking
For example, to determine if a lexeme is a valid
identifier in C, we could use the following regular
expression: [a-zA-Z ][a-zA-Z 0-9]∗ This regular
expression says that identifiers must begin with a
Roman letter or an underscore and may be followed
by any number of letters, underscores, or numbers
20. CONCLUSION
Both regular expressions and finite-state automata
represent regular languages.
The basic regular expression operations are:
concatenation, union/disjunction, and Keene closure.
The regular expression language is a powerful pattern-
matching tool.
Any regular expression can be automatically compiled
into an NFA, to a DFA, and to a unique minimum-state
DFA.
An FSA can use any set of symbols for its alphabet,
including letters and words.