Recent questions tagged goclasses-cs-dpp-day-378

Let $L$ be a context-free language and $R$ be a regular language.Consider the problem$$L-R=\varnothing?$$Which statement is correct?It is decidable because $L-R$ is conte...

For a language $L$, define$$L^R=\{w^R\mid w\in L\}.$$ If $L$ is context-free, which statement is correct?$L^R$ is always regular. $L^R$ is always context-free. $L^R$ may ...

Suppose a language $L$ is accepted by some pushdown automaton.What can always be concluded about $L^*$?$L^*$ must be regular. $L^*$ must be context-free. $L^*$ need not b...

Let $R$ be a regular language and $C$ be a context-free language over the same alphabet.Which statement about $R\cup C$ is always true?$R\cup C$ must be regular. $R\cup C...

The class of context-free languages satisfies which one of the following?It is closed under intersection. It is closed under complementation. It is closed under concatena...

Assume the expressions below are schema-valid and relations use set semantics.Which of the following are always true?$(\mathrm{R}\bowtie\mathrm{S})\bowtie\mathrm{T}=(\mat...

Consider the relations:$\mathrm{Authors(au\_id,au\_lname,au\_fname,phone,address,city,state,zip)}$$\mathrm{TitleAuthors(au\_id,title\_id,au\_ord,royaltyshare)}$$\mathrm{T...

Consider the relations:$\mathrm{Locations(locationid,name,state,altitude)}$ and $\mathrm{FallColors(week,year,locationid,color,peakpercent)}$.We want locations in New Y...

Consider the relations:$\mathrm{Posts(pid,folder,summary)}$ and $\mathrm{Postings(post,position,user,ptext)}$.Let $\mathrm{R_1}$ and $\mathrm{R_2}$ be two renamed copies ...

Consider the relation:$\mathrm{Marks(studentID,~courseID,~courseType,~score)}$Let, $\mathrm{M_1=\rho_{M_1}(Marks)}$ and $\mathrm{M_2=\rho_{M_2}(Marks)}$.Which expression ...