Extended BNF

Optional constructs written as [ x ]

Zero or more of x written as { x }

Choice (“or”) written using |

Grouping with parentheses ( x | y ) as in { (x | y ) z }

<expression> ::= <term> { (+ | -) <term> }

<term> ::= <factor> { (* | /) <factor> }

<factor> ::= ’(’ <expression> ’)’ | name | number

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