Exam-style question
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What does the symbol ::= usually mean in a BNF production rule?.
- A.Is defined as
- B.Must be repeated exactly twice
- C.Is optional
- D.Ends the language
Model answer
What a good answer should say
- Is defined as
Explanation
Why this works
The symbol ::= separates a non-terminal from the alternatives or sequence that define it. For example, <digit> ::= "0" | "1" means that <digit> is defined as either "0" or "1".
Common mistake
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