Re: puzzling Octave behaviour

[Francesco Potorti`]

>The real problem is that testing doubles for equality doesn't 
>work very well. It doesn't have anything to do with Octave, it's 
>just a property of the floating point representation that 
>computers use. You need to test to see if the numbers are close, 
>within some tolerance, like (a - b) < 1e-10, instead of a == b.

You example is wrong, because it should use abs().

Moreover, it assumes that you know the range of values of a and b.  For
example, it gives wrong results if a and b are in the order of 1e-10.  A
better test would be something like

 abs(a-b) < 10*abs(a)*eps

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