November 4, 2009

    public static void main (String[] args) {
        int[] foo = new int[1];
        int[] bar = new int[1];
        ((args.length == 0) ? foo[0] : bar[0]) = 1;
    }

2 Responses to “Thank Gosling”

1. wtfwtf_ok says:

   November 5, 2009 at 9:03 am

   The 2nd and 3rd operands to the ternary operator must be values, not variables.

   Your particular example could be done similarly as:

   // legal
   ((args.length == 0) ? foo : bar)[0] = 1;

   But:

   // not legal
   ((args.length == 0) ? foo : bar) = new int[1];
2. mdb says:

   November 5, 2009 at 9:57 am

   Yeah, that turns out to be very useful for my current purposes, which is that I have an AST and I’m looking at the assignment operator and I want to know of the left-hand side is an array select or not. Clearly the left child of the AST could just be an array select and I’m fine, but I was wondering when I might need to traverse the left-tree to go looking for a select.

   I believe that the only time I need to do that is if the left-hand side is a Paren node. The following is legal:

   (foo[3]) = 5;

   But AFAIK the only thing I need to worry about is parens. No other expression on the left-hand side can evaluate to a variable into which I will store a value. Probably I’m missing something. :)