> "it is not known whether these numbers equal each other" Equality, among other operations, are not defined for these inputs. NaN's really are a separate typ

> "it is not known whether these numbers equal each other" Equality, among other operations, are not defined for these inputs. NaN's really are a separate type of object embedded inside another objects value space. So you get the rare programmers gift of being able to construct a statement that is not always realizable based solely on the values of your inputs.