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Date: Mon, 24 Oct 2005 04:27:08 +0200 From: Marcin 'Qrczak' Kowalczyk <qrczak@xxxxxxxxxx> Taylor Campbell <campbell@xxxxxxxxxx> writes: > this is typically what is done with exact arithmetic, such as in > Scheme48: > > (/ 0 0) => Error: rational division by zero Of course; because in the case of exact arithmetic the problem definitely means that the function is undefined at this point. With inexact arithmetic it might just result from rounding errors, so a computation can't expect it in advance, thus it's not generally a symptom of a bug. Conditions do not imply bugs. They are just that: conditions. How they are detected is a matter unrelated to their fundamental purpose. NaN is a condition, just like the end of an input stream; it's not an actual numerical value, though it is produced as a result of IEEE 754 numerical operations, just as an EOF object is not any element of an input stream but is produced by procedures that read from them; and neither necessarily implies a bug in a program.