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'''--[[User:Manus|manus]] 19:37, 8 May 2007 (CEST)''': Have a look at [[Real_numbers| Real Numbers]] page where we already started a similar discussion but currently only for the specification of REAL_64, not its usage.

== One possibility for working with NaN ==

I was working on a project to represent complex numbers and used the following `is_equal' to accomodate the use of NaNs:

<e>
	is_equal (other: like Current): BOOLEAN
			-- Is `other' attached to an object considered
			-- equal to current object?
			-- If current object is not a number (NaN) and
			-- `other' is as well `True' will be returned.
		do
			if is_nan then
				if real /~ real and then imaginary ~ imaginary then
					Result := real /~ other.real and then imaginary ~ other.imaginary
				elseif real ~ real and then imaginary /~ imaginary then
					Result := real ~ other.real and then imaginary /~ other.imaginary
				elseif real /~ real and then imaginary /~ imaginary then
					Result := real /~ other.real and then imaginary /~ other.imaginary
				end
			else
				Result := real ~ other.real and then imaginary ~ other.imaginary
			end
		end
</e>

--[[User:Colin-adams|Colin-adams]] 10:17, 22 February 2010 (UTC) Can you format that code? I can't follow it at all as it stands.

---[[User:Peter gummer|Peter gummer]] 14:44, 22 February 2010 (UTC): Whoever pasted the code there had formatted it, but without suitable mark-up it came out on one line. I've added the mark-up ... how's that look now?

--[[User:Colin-adams|Colin-adams]] 14:27, 23 February 2010 (UTC)So that is pretending that two NaNs compare equal. Which is unsound. you are saying that the complex numbers (0/0, 1) and (0/0, 1) are equal. The whole problem arises because they are not comparable.

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