# Difference between revisions of "Talk:Not a Number"

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

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is_equal (other: like Current): BOOLEAN | is_equal (other: like Current): BOOLEAN | ||

-- Is `other' attached to an object considered | -- Is `other' attached to an object considered | ||

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end | end | ||

end | end | ||

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+ | --[[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. | ||

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+ | ---[[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? | ||

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+ | --[[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. |

## Latest revision as of 06:27, 23 February 2010

**--manus 19:37, 8 May 2007 (CEST)**: Have a look at 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:

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

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

---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?

--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.