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Date: Sun, 23 Oct 2005 22:18:40 -0500 From: Alan Watson <a.watson@xxxxxxxxxxxxxxxx> Taylor Campbell wrote: > I think it's > pretty plain & straightforward that what NaN represents is not a > number due to an undefined mathematical operation. Can you elaborate > on what you meant here? The IEEE flonum standard precisely defines the conditions under which NaNs are produced. For example, in conventional arithmetic, zero divided by zero is not defined, but in IEEE flonum arithmetic, zero divided by zero is defined to yield a NaN. It is defined for the sake of computational convenience; what NaN denotes mathematically is the condition of an undefined operation, even if it exists as a value that IEEE flonum operations can produce. There is a distinction between mathematical definedness and IEEE specification for pragmatic reasons.