Backus Normal/Nauer Form example

bnf_example

<program>                          ::= <statement_list>
<statement_list>                   ::= <variable_def> 
                                               | <assignment_statement> 
                                               | <conditional_statement> 
                                               | <loop_statement> 
                                               | <block_statement>
                                               | <variable_def> <statement_list>
                                               | <assignment_statement> <statement_list>
                                               | <conditional_statement> <statement_list>
                                               | <loop_statement> <statement_list>
                                               | <block_statement> <statement_list>
<variable_def>                     ::= def <id> : <type>;
<assignment_statement>             ::= <id> = <expression_list>;
<expression_list>                  ::= <math_expression> 
                                                | <math_expression> <math_operator> <math_expression>
                                                | <function>
<condition_statement>              ::= if [<bool_statement>] then <block_statement>
<bool_statement>                   ::= !<bool_statement>
                                                  | <conditional_expression>
<conditional_expression>           ::= <math_expression> <relational_operator> <math_expression>
<math_expression>                  ::= <digit_list> 
                                                 | (<math_expression>)
                                                 | <math_expression> <math_operator> <math_expression>
<loop_statement>                   ::= while [<conditional_statement>] <block_statement>
<block_statement>                  ::= {};
                                                   | { <statement_list> };
<math_operator>                    ::= ‘+’ | ‘-’ | ‘*’ | ‘/’ | ‘^’ | ‘%’
<relational_operator>              ::= ‘=’ | ‘!=’ | ‘<’ | ‘>’ | ‘<=’ | ‘>=’
<function>                         ::= <id>();
<id>                               ::= <character_list>
<character_list>                   ::= <character>
                                                   | <character> <character_list>
<character>                        ::= <letter> | <number>
<letter>                           ::= ‘a’ | ‘b’ | ‘c’ | ‘d’ | ‘e’ | ‘f’ | ‘g’ | ‘h’ | ‘i’ | ‘j’ | ‘k’ | ‘l’
                                                   | ‘m’ | ‘n’ | ‘o’ | ‘p’ | ‘q’ | ‘r’ | ‘s’ | ‘t’ | ‘u’ | ‘v’ | ‘x’
                                                   | ‘y’ | ‘z’ | ‘A’ | ‘B’ | ‘C’ | ‘D’ | ‘E’ | ‘F’ | ‘G’ | ‘H’ | ‘I’ 
                                                   | ‘J’ | ‘K’ | ‘L’ | ‘M’ | ‘N’ | ‘O’ | ‘P’ | ‘Q’ | ‘R’ | ‘S’ 
                                                   | ‘T’ | ‘U’ | ‘V’ | ‘X’ | ‘Y’ | ‘Z’
<signed_number>                     ::= ‘-’ <number>
                                                   | <number>
<number>                            ::= ‘0’ | ‘1’ | ‘2’ | ‘3’ | ‘4’ | ‘5’ | ‘6’ | ‘7’ | ‘8’ | ‘9’ 
<digit_list>                        ::= <signed_number>
                                                  | <signed_number> <digit_list>