TOC book ACE

Question

If w is a string and wR is reverse of it then what language it wull satisfy if I concatenate like w.wR ? Is it regular of cfl ?

Comments

should be CFL, it accepted by NPDA.

check this https://gateoverflow.in/222710/pda-doubt

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Here .(dot) means concatenation or is it a symbol from the alphabet?

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@sakharam

read the question clearly, it means concatenation only

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I thought so but lets say the new language has . as a part of the alphabet {a,b,.} assuming a and b the symbols were in the previous language. :-)

In this case it would have been Deterministic CFL

Thanks for the clarification

Answer 1

w= regular(dfa) and $w^{r}$= regular(dfa)  w.$w^{r}$ also a dfa

Comments

your answer is wrong because there is a need of comparison between w and $w^{r}$ so it can't be handle by dfa,.