In formal language theory, a context-free language (CFL) is a language generated by some context-free grammar (CFG). The set of regular languages is a subset of the set of context-free languages.
Questions tagged [context-free-language]
183 questions
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Is L = {a^mb^nc^k | if (m=n) then (n=k) } CFL or not?
I see that in this language , by the time we are deciding m=n; then we have no b's left; so we can't sompare them with c's.So, i think it should NOT be CFL.
But below solution shows that it is CFL
In the above given solution, is L2 CFL correct ?
Olivia Pearls
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Generating Grammar from Language
While there are enormous resources to convert a CFG(Context Free Grammar) to language, there isn't any resource to create a CFG out of a given sentence. Basically, I am trying to use the grammar to do a CKY parsing and generate tree.
Currently, If…
YaArj
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Construct a grammar over {a,b} whose language is
Construct a grammar over {a,b} whose language is
{a^m b^n | 0 <= n <= m <= 3n}
I am not sure how to go about this problem, I started out by doing
n >= 0
m >= n
3n >= m
S -> a S b | a S bb
raywrigh
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Describe the language generated by this context-free grammar
I have the following grammar,
S -> Sb
S -> aaSb
S -> b
The typical derivations in this grammar are
S => Sb => [aaSb]b => [aa[b]b]b => aabbb for n = 1
S => Sb => [aaSb]b => [aa[aaSb]b]b => [aa[aabb]b]b => aaaabbbb for n = 2
Edit:
So I claimed…
Storage Lenovo
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I have seen two questions, and I don't know how to answer this
Is the language of strings which are not of the form t#t, where t is an arbitrary string over {0,1} a CFL? I don't know to solve this.
Another question is that: Is the set consisting of: production rules of Grammers that are CFGs, itself a regular…
Kitchen
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Proving that the set difference of a CFG and a regular language is also context free
I need help proving the set difference between a context free grammar A and a regular language, B, is a context free language.
I'm trying to prove by example like this:
Let A = {a^n b^n | n >= 1}
Let B = {w {a,b}* | w has atleast three a's }
Then…
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How to prove a Language is NOT Context Free
I've been watching a lot of videos about how to prove this and I am getting mixed information about how to do so.
In the case of contradiction, I am getting two different approaches and I want to know which is correct.
Example:
L = {a^n b^n+1…
msc
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How to convert cfg to pda with 2 states?
i'm running into some problem for my research in computer science theories...
Can any one explain me the algorithm that how we can convert a context-free grammar(cfg) to corresponding push down automata(pda)
With just 2 state ?
Shahin Ghasemi
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Constructing a linear grammar for the language
I find difficulties in constructing a Grammar for the language especially with linear grammar.
Can anyone please give me some basic tips/methodology where i can construct the grammar for any language ? thanks in advance
I have a doubt whether the…
Ejaz Ahamed
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Context-free grammar for L = {2^x ∗ 2^y ∗ 2^z = 2^(x+y+z) | x, y, z > 0}
The title explains it. I have trouble with synchronizing the left side of the "equation" with the right one, as whenever I generate a 2 on the left, one on the right has to appear. Could it be that this language isn't context-free?
Thanks in…
Nanuna
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What does CFG production rule look like in code?
There is so much info out there but non of this really helps a noob like me. I read a lot of articles about context-free-languages and pushdown automation. Now im trying to understand how certain things might look in code.
Lets assume we defined a…
Asperger
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Is this context free language regular?
If I have a language {0,1} defined by the following context-free grammar with start variable S, is it a regular language?
S→TS, S→1T, S→1S
T→TT, T→0T1, T→1T0 T→ε
Is this language regular?
It seems to me that this language cannot be regular because…
Archeofuturist
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Context free and regular language with push-down automata and infinite elements
I was doing my HW assignment for my theory class and came across a problem that I don't really even know where to begin. We are covering the section of Push-Down automata.
"Let L1 be a context-free language and L2 be regular. Show that there exists…
Reaperr
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Why regular languages should not have unit rules Variable -> Variable?
I was reading about regular languages. I did not understand one thing.
Why
Variable -> Variable is not allowed ?
What is the reasoning behind it ?
What happens if there is such a rule ? What kind of grammar does it become ?
Harish Kayarohanam
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Check if word is part of contextfree language
Good evening to all!
As a fan of regular expressions in Perl, I came up with a question, which I could not answer by googling and searching for myself.
So let me give you a minimal example of my problem:
I have two…
Otterbein
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