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BNF Rules

• A rule has a left-hand side (LHS) and a right-hand side (RHS), and consists of terminal and nonterminal symbols

• A grammar is a finite nonempty set of rules

• An abstraction (or nonterminal symbol) can have more than one RHS:

      <stmt> -> <single_stmt> 
              | begin <stmt_list> end
  

• Syntactic lists are described using recursion:

      <ident_list> -> ident
                    | ident, <ident_list>