} else if (expr instanceof E_Divide) {
expr.getArg1().visit(this) ;
expr.getArg2().visit(this) ;
Expression e2 = expression.pop();
Expression e1 = expression.pop();
expression.push(new Divide(e1, e2));
} else if (expr instanceof E_Equals) {
convertEquals((E_Equals) expr);
} else if (expr instanceof E_NotEquals) {
convertNotEquals((E_NotEquals) expr);
} else if (expr instanceof E_LangMatches) {