expression		-> equality

equality		-> comparison ( ( "==" | "!=" ) comparison )* ;
comparison		-> term ( ">" | ">=" | "<" | "<=" term )* ;
term			-> factor ( ( "+" | "-" ) factor )*
factor			-> unary ( ( "*" | "/" ) unary )* ;
unary			-> ( "!" | "-" ) unary | primary ;
primary			-> "(" expression ")" | NUMBER | STRING | "true" | "false" | "nil" ;