I actually avoided going that far to avoid getting bad data. I was trying to answer the question, "What does the experimenter THINK his rule is?" rather than what will the computer do. Since the computer can't be infinite, it will inevitably fail with overflow, underflow, and such.

I was relieved, in fact, when it worked with negatives and floats in a "safe" range.

I also tested with 1,1,2 and 1,2,2 to make sure that the required increase applied to ALL of the values, not just a specific pair.

I too tried to test if it was only one pair that was significant. However I grew impatient and didn't try to come up with more tests when I thought I had a sufficient answer to explain my most vexing observation (negative, positive, positive out of combinations involving negative numbers).

The observation to brainstorm for ways of proving that a statement is in fact wrong, and exhausting them, is such an eloquent way of wording the hunt for a negative.

The slightly-shorter 0.60000000000000000, 0.60000000000000001, 0.60000000000000002 will break it too, for what it's worth. If you punch those in to a Javascript console, you can see that the FP representation of all three is 0.6.

0.20000000000000000, 0.20000000000000001, 0.20000000000000002 also work.

Hah! Nice catch.

Pentester. :)