如何构建生成语言L的语法？

Question

I'm in a Formal languages class and have a grammar quiz coming up. I'm assuming something like this will appear.

Consider the alphabet ∑ = {a, b, c}. Construct a grammar that generates the language L = {bab^nabc^na^p : n ≥ 0, p ≥ 1}. Assume that the start variable is S.

Answer 1

It was a very long time since I worked with formal languages for the last time, so, please, forgive my rustyness, but this would be the language: We divide S to a prefix variable ( A ) and a suffix variable ( B ). Then, we handle the prefix and the suffix separately, both of them have a possible rule of further recursion, and an end sign of empty, where no occurrence is required and the constant where at least an occurrence is required.

{bab^nabc^na^p : n ≥ 0, p ≥ 1}

S -> ASB
A -> babAabc
A -> {empty}
B -> Ba
B -> a