statement ::= statement ";" statement
statement ::= "if" boolExpression "then" statement "end"
statement ::= "while" boolExpression "do" statement "done"
statement ::= "print" expression

expression ::= "(" expression ")"
expression ::= term ( "+" | "-" ) term
expression ::= term

term ::= primary ( "*" | "/" | "%" ) primary
term ::= primary

primary ::= identifier | integer

boolExpression ::= "true" | "false"
boolExpression ::= relationExpression

relationExpression ::=
    expression ( "=" | "!=" | ">" | "<" | ">=" | "<=" ) expression

identifier ::= alpha { alphanum }

alpha ::= one of a-z

alphanum ::= alpha | digit | "_"

integer ::= integer digit | digit

digit ::= one of 1-9