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This looks very much like NULLs in the SQL world. A null (and NaN) is like an unknown. One can't compare unknowns because they are exactly that, unknown. Let

This looks very much like NULLs in the SQL world. A null (and NaN) is like an unknown. One can't compare unknowns because they are exactly that, unknown. Let's construct a language that on division on zero returns unknowns. a = 5 / 0; b = 10 / 0; Now, both a and b are set to unknown state. If one were to compare a to b, should the expectation be that they hold same value? I wish all languages would have nullability like SQL does. Where a great care has to be given to deal with nullable data, lest nulls nullify everything.

malkia 14y ago
In some languages, a, b would be +Infinity. On top of my head I can't remember whether +Infity != +Infinity (have to write a test and see). For NaN's definitely.
- tikhonj 14y ago
  One of those languages is JavaScript, so--assuming your browser supports JavaScript--you do have somewhere to test it :P. The answer is that 5 / 0 is Infinity and (5 / 0) == (5 / 0), so it's all good :). Now, 0 / 0 is NaN and (0 / 0) != (0 / 0).