On Thu, Apr 8, 2010 at 7:58 PM, wren ng thornton
They don't? I am pretty sure that a floating point number is always equal to itself, with possibly a strange corner case for things like +/- 0 and NaN.
Exactly. NaN /= NaN.
Other than that, I believe that "let x = ... in x == x" is true (because they are the same bitfield by definition), however it is easy to have 'the same number' without it having the same bitfield representation due to loss of precision and the like. To say nothing of failures of other laws leading to overflow, underflow, etc.
Indeed. NaN means that equality is not reflexive for floats in general, only a subset of them. Likewise, addition and multiplication are not associative and the distributive law doesn't hold. I think commutativity is retained, though. That's something, right? - C.