Regular Expressions

Question 1

what are regular expressions

Answer 1

a way of descfribing a set that allows particular types of languages to be described in a shorthand notation

Question 2

what does the following symbol mean

a

Answer 2

a symbol has to be used

Question 3

what does the following symbol mean

*

Answer 3

0 or more repetitions

Question 4

what does the following symbol mean

+

Answer 4

1 or more repititions

Question 5

what does the following symbol mean

?

Answer 5

0 or 1 repititions (optional)

Question 6

what does the following symbol mean

|

Answer 6

or

Question 7

what does the following symbol mean

()

Answer 7

groups regular expressions

Question 8

what does the following symbol mean

[abc]

Answer 8

a or b or c

Question 9

what does the following symbol mean

[^jkl]

Answer 9

any character except j, k or l

Question 10

what does the following symbol mean

[a-z]

Answer 10

any character in lowercase

Question 11

write a list of some valid inputs for a(a|b)

Answer 11

• a
• aaaaaa
• ab

Question 12

True or False

the set of strings defined by a regular language is always finite in size

Answer 12

False

Question 13

write a regular expression that matches either clare or claire

Answer 13

clai?re

Question 14

write a regular expression that matches

• starts with 10
• has zero or more occurences of any combination of 0 or 1 in the middle
• ends with 01

Answer 14

10(0|1)*01