Homework Help is Here – Start Your Trial Now!
Engineering
Computer Engineering
2.1 Write regular expression for the following character sets, or reasons why no regular expression can be written: a. All strings of lowercase letters that begin and end in a. b. All strings of lowercase letters that either begin or end in a both) c. All strings of digits that contain no leading zeros d. All strings of digits that represent even numbers

2.1 Write regular expression for the following character sets, or reasons why no regular expression can be written: a. All strings of lowercase letters that begin and end in a. b. All strings of lowercase letters that either begin or end in a both) c. All strings of digits that contain no leading zeros d. All strings of digits that represent even numbers

Computer Networking: A Top-Down Approach (7th Edition)
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
See similar textbooks
icon
Related questions
Question
### Regular Expression Exercise #### 2.1 Write a regular expression for the following character sets, or provide reasons why no regular expression can be written: a. **All strings of lowercase letters that begin and end in `a`.** b. **All strings of lowercase letters that either begin or end in `a` (or both).** c. **All strings of digits that contain no leading zeros.** d. **All strings of digits that represent even numbers.** #### Explanation: **a**: For strings that begin and end with `a`, the regular expression can be: ``` ^a[a-z]*a$ ``` Here, `^` asserts the position at the start of a line, `a` matches the start character, `[a-z]*` matches zero or more lowercase letters, and `a$` matches the last character and asserts position at the end of a line. **b**: For strings that either begin or end with `a` (or both), the regular expression can be: ``` (^a[a-z]*$)|(^[a-z]*a$) ``` This combines two conditions: strings that begin with `a` or those that end with `a`. **c**: For strings of digits that contain no leading zeros, the regular expression can be: ``` ^[1-9][0-9]*$ ``` Here, `^` asserts the position at the start of a line, `[1-9]` matches any digit from 1 to 9 (ensuring no leading zero), and `[0-9]*` matches zero or more digits. **d**: For strings of digits that represent even numbers, the regular expression can be: ``` ^[0-9]*[02468]$ ``` This matches any sequence of digits ending in 0, 2, 4, 6, or 8, which represent even numbers. ### Notes: - For part c, a string containing only "0" is not specified, but typically, "0" would be considered a special case. - The regular expressions are written considering that `^` and `$` are used to assert the start and end of lines, respectively.
Transcribed Image Text:### Regular Expression Exercise #### 2.1 Write a regular expression for the following character sets, or provide reasons why no regular expression can be written: a. **All strings of lowercase letters that begin and end in `a`.** b. **All strings of lowercase letters that either begin or end in `a` (or both).** c. **All strings of digits that contain no leading zeros.** d. **All strings of digits that represent even numbers.** #### Explanation: **a**: For strings that begin and end with `a`, the regular expression can be: ``` ^a[a-z]*a$ ``` Here, `^` asserts the position at the start of a line, `a` matches the start character, `[a-z]*` matches zero or more lowercase letters, and `a$` matches the last character and asserts position at the end of a line. **b**: For strings that either begin or end with `a` (or both), the regular expression can be: ``` (^a[a-z]*$)|(^[a-z]*a$) ``` This combines two conditions: strings that begin with `a` or those that end with `a`. **c**: For strings of digits that contain no leading zeros, the regular expression can be: ``` ^[1-9][0-9]*$ ``` Here, `^` asserts the position at the start of a line, `[1-9]` matches any digit from 1 to 9 (ensuring no leading zero), and `[0-9]*` matches zero or more digits. **d**: For strings of digits that represent even numbers, the regular expression can be: ``` ^[0-9]*[02468]$ ``` This matches any sequence of digits ending in 0, 2, 4, 6, or 8, which represent even numbers. ### Notes: - For part c, a string containing only "0" is not specified, but typically, "0" would be considered a special case. - The regular expressions are written considering that `^` and `$` are used to assert the start and end of lines, respectively.
Expert Solution
trending now

Trending now

This is a popular solution!

steps

Step by step

Solved in 2 steps

SEE SOLUTIONCheck out a sample Q&A here
Blurred answer
Recommended textbooks for you
Computer Networking: A Top-Down Approach (7th Edi…
Computer Networking: A Top-Down Approach (7th Edi…
Computer Engineering
ISBN:
9780133594140
Author:
James Kurose, Keith Ross
Publisher:
PEARSON
Computer Organization and Design MIPS Edition, Fi…
Computer Organization and Design MIPS Edition, Fi…
Computer Engineering
ISBN:
9780124077263
Author:
David A. Patterson, John L. Hennessy
Publisher:
Elsevier Science
Network+ Guide to Networks (MindTap Course List)
Network+ Guide to Networks (MindTap Course List)
Computer Engineering
ISBN:
9781337569330
Author:
Jill West, Tamara Dean, Jean Andrews
Publisher:
Cengage Learning
Concepts of Database Management
Concepts of Database Management
Computer Engineering
ISBN:
9781337093422
Author:
Joy L. Starks, Philip J. Pratt, Mary Z. Last
Publisher:
Cengage Learning
Prelude to Programming
Prelude to Programming
Computer Engineering
ISBN:
9780133750423
Author:
VENIT, Stewart
Publisher:
Pearson Education
Sc Business Data Communications and Networking, T…
Sc Business Data Communications and Networking, T…
Computer Engineering
ISBN:
9781119368830
Author:
FITZGERALD
Publisher:
WILEY
SEE MORE TEXTBOOKS