NaNs have an odd ontology, regardless of what they claim to be. For example, hypot(Inf, NaN) == Inf (C99), which suggests that NaN is "some number but we canno

NaNs have an odd ontology, regardless of what they claim to be. For example, hypot(Inf, NaN) == Inf (C99), which suggests that NaN is "some number but we cannot know what it is".