calc.loli.txt

ignore whitespace = "[ \t\r\n]+";
token int = "[0-9]+";
token op_add = "\+";
token op_minus = "-";
token op_asterisk = "\*";
token op_slash = "/";
token lp = "\(";
token rp = "\)";
token comma = ",";

enum BinaryOp { Plus; Minus; Asterisk; Slash; }

base Expression;

node LiteralExpression : Expression
{
    token value;
}

node BinaryExpression : Expression
{
    Expression lhs;
    BinaryOp op;
    Expression rhs;
}

rule AddOp : BinaryOp
    = op_add -> Plus
    = op_minus -> Minus
    ;
rule MulOp : BinaryOp
    = op_asterisk -> Asterisk
    = op_slash -> Slash
    ;

rule Factor : Expression
    = int:value -> LiteralExpression
    = lp Expr! rp
    ;
rule MulExpr : Expression
    = MulExpr:lhs MulOp:op Factor:rhs -> BinaryExpression
    = Factor!
    ;
rule AddExpr : Expression
    = AddExpr:lhs AddOp:op MulExpr:rhs -> BinaryExpression
    = MulExpr!
    ;

rule Expr : Expression
    = AddExpr!
    ;