type of given language ?

Question

let P,Q,R be three languages. if P nd R are regular and if PQ=R the Q is ?

Comments

repeated..

Answer 1

Q can be anything

Take P as ∅

∅L = ∅

so, L can be anything

Answer 2

Let the operation is concatenate. as no operation is given . i think we should consider it as concatenate. so Q may or may no be regular for ex . p=X | x∈(a+b)* now assume that q be a language ww. w belong to the same domain as x. so now the new language p.q= L={xww∣w,x∈(a+b)∗}

xww  which will be regular. q may or may not be regular and cfl . it can be csl also..

for more .:http://gatecse.in/wiki/Identify_the_class_of_the_language