%token <int> INT%token PLUS MINUS TIMES DIV UMINUS%token LPAREN RPAREN%token EOL EOF %left PLUS MINUS        /* lowest precedence */%left TIMES DIV         /* medium precedence */%nonassoc UMINUS        /* highest precedence */  %type <int> Expr %start Main             /* the entry point */%type <int> Main %% Main:    Expr EOL                { $1 };Expr:    INT                     { $1 }  | LPAREN Expr RPAREN      { $2 }  | Expr PLUS Expr          { $1 + $3 }  | Expr MINUS Expr         { $1 - $3 }  | Expr TIMES Expr         { $1 * $3 }  | Expr DIV Expr           { $1 div $3 }  | UMINUS Expr             { ~ $2 };