// arithmetic expressions

lines		: [{ [ sum ] "\n" }];
sum		: product [{ sum.add | sum.sub }];
sum.add		: "+" product;
sum.sub		: "-" product;
product		: term [{ product.mul | product.div | product.mod }];
product.mul	: "*" term;
product.div	: "/" term;
product.mod	: "%" term;
term		: Number | "+" term | term.minus | "(" sum ")";
term.minus	: "-" term;