The Gateway to Computer Science Excellence
For all GATE CSE Questions
Toggle navigation
Email or Username
Password
Remember
Login
Register

I forgot my password
Activity
Questions
Unanswered
Tags
Subjects
Users
Ask
Prev
Blogs
New Blog
Exams
Intersection and concatenation in CFG
0
votes
372
views
Given that L1 is regular and L2 context free.
i) L3 = L1 ∩ L2
ii) L4= L1.L2
Selct the most appropriate statement:
a. L3 , L4 are regular
b. L3 is regular L4 is CFG not regular
c. L3 is CFG, not regular L4 is regular
d. L3,L4 are CFG not regular
theoryofcomputation
asked
Feb 1, 2017
in
Compiler Design
by
sh!va
Boss

372
views
answer
comment
0
is it D?
Please
log in
or
register
to add a comment.
Please
log in
or
register
to answer this question.
1
Answer
+1
vote
Best answer
Option D) is almost correct.
1) Intersection of CFL and regular is CFL but it may be regular too. For eg if L1 is $\epsilon$ which is regular then intersection of L1 with any langauage will be $\epsilon$ which is regular. So it is defintely CFL and may or may not be regular
2) Similarly concatenation is also closed for CFL. but in certain cases it may be regular. If L1 = $\phi$ then concatenation with always be phi which is regular.
So both are definetely CFL and may or may not be regular.
answered
Feb 1, 2017
by
Kaushik.P.E
Active
selected
Feb 1, 2017
by
sh!va
comment
Please
log in
or
register
to add a comment.
← Prev.
Next →
← Prev. Qn. in Sub.
Next Qn. in Sub. →
Related questions
0
votes
0
answers
1
Turing Machine for concatenation of strings w1 and w2 where w1, w2 belongs to {a,b} using single tape
asked
Oct 31, 2017
in
Theory of Computation
by
ashwina
Active

908
views
theoryofcomputation
turingmachine
+3
votes
1
answer
2
DFA  Union and Intersection
Please explain the UNION and the INTERSECTION of two DFAs with suitable examples. I looked over the internet and I'm not satisfied with any of the explanations I came across.
asked
Aug 28, 2017
in
Theory of Computation
by
Akash Mishra
Active

2k
views
theoryofcomputation
finiteautomata
0
votes
2
answers
3
If L=(a+b)* and R=a*b*a* then L intersection R=?
We know, here R subset L so by formula R intersection L= R, but for any string R=L( both language are same) R intersection L can be R or L? Correct me!
asked
Jan 12, 2017
in
Theory of Computation
by
smartmeet
Active

188
views
theoryofcomputation
regularlanguages
settheory&algebra
0
votes
0
answers
4
Concatenation of DCFLs
L1={an bn  n>=0} L2={bn cn  n>=0} What is L1.L2 ? Is it an b2n cn ?
asked
Oct 13, 2018
in
Theory of Computation
by
sripo
Active

82
views
theoryofcomputation
dcfl
contextfreelanguages
identifyclasslanguage
Quick search syntax
tags
tag:apple
author
user:martin
title
title:apple
content
content:apple
exclude
tag:apple
force match
+apple
views
views:100
score
score:10
answers
answers:2
is accepted
isaccepted:true
is closed
isclosed:true
Recent Posts
GATE Overflow Test Series  GATE CSE 2021
IIT gandhinagar mtech cse2020
IIT Delhi Research Interview Shortlists out
IIT Gandhinagar interview experience
IIT Gandhinagar Interview 2020
Subjects
All categories
General Aptitude
1.9k
Engineering Mathematics
8.2k
Digital Logic
2.9k
Programming and DS
5k
Algorithms
4.4k
Theory of Computation
6.2k
Compiler Design
2.2k
Operating System
4.6k
Databases
4.2k
CO and Architecture
3.4k
Computer Networks
4.2k
Non GATE
1.2k
Others
1.5k
Admissions
595
Exam Queries
562
Tier 1 Placement Questions
23
Job Queries
71
Projects
19
Unknown Category
1k
Recent Blog Comments
Verification will automatically expire after 400...
My Verification is showing as "Not verified Yet"...
The point calculation formula is changed. We were...
Keep doing problems. Chances are high that you...
The price will be the same till June 30th.
Network Sites
GO Mechanical
GO Electrical
GO Electronics
GO Civil
CSE Doubts
52,215
questions
59,981
answers
201,180
comments
94,636
users