Exam-style question
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Why can BNF represent some languages that cannot be represented using regular expressions?.
- A.BNF can use recursive production rules, allowing structures such as arbitrarily nested pairs
- B.BNF always uses fewer symbols than a regular expression
- C.BNF automatically checks whether every character is typed correctly
- D.BNF can represent only languages with a fixed maximum length
Model answer
What a good answer should say
- BNF can use recursive production rules, allowing structures such as arbitrarily nested pairs
Explanation
Why this works
A recursive BNF rule can refer to itself and so describe structures with unlimited nesting, such as balanced parentheses. Regular expressions cannot represent every such language.
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