[dchapp]

> I'm sorry addition isn't commutative...

My understanding is that in IEEE 754 compliant implementations of floating-point arithmetic, commutativity over "+" holds but not associativity. (With the possible exception to commutativity for the NaNs, though I don't remember offhand whether this caveat is necessary).

[taylodl]

You are correct. It's associativity that doesn't hold, not commutativity. It really throws people off.