How to use BNF for {a^n b^n | n>0}

Question

so I know that this language is not regular, however, can you still define the language using BNF? This is the problem:

{a^n b^n |n>0}

Answer 1

This is a classic example of a context-free language. See How to prove that a language is context-free? for how to find the corresponding context-free grammar. Then once you have a context-free grammar, you can write it down in BNF.