Why does .NET 4.0 sort this array differently than .NET 3.5?

Question

This stackoverflow question raised an interesting question about sorting double arrays with NaN values. The OP posted the following code:

static void Main(st         


        

Answer 1

I don't have the code for the .NET 3.5 runtime to verify this, but I'm thinking they fixed a bug in the default comparer for double to bring it into line with the documentation.

According to that document, Double.Compare treats NaN as equal to PositiveInfinity and NegativeInfinity, and less than any other value.

The documentation is the same for .NET 3.5 and .NET 4.0, so I have to think that this was a bug fix to make the code work as documented.

EDIT:

After reading the comments in the linked question, I have to think that the problem wasn't in Double.Compare, but rather in whatever method Array.Sort (which is what List.Sort depends on) uses to compare Double values. Somehow, I don't think it's really Double.Compare.