public CompareExp(Exp l, Token op, Exp r)
{
Left = l;
Right = r;
switch(op.Type){
case TokenType.LT:
Oper = Operator.LT;
break;
case TokenType.GT:
Oper = Operator.GT;
break;
case TokenType.EQ:
Oper = Operator.EQ;
break;
case TokenType.LE:
Oper = Operator.LE;
break;
case TokenType.GE:
Oper = Operator.GE;
break;
}
}