double compare 0.2 != 0.2 How?

[Curtis Rutland]

Most of my work thus far hasn't had much to do with floating point precision, I'm sure I would have found some of that info if I was ever required to.

[vekipeki]

That is how things work, the only thing you can do is add a handy extension method to System.Double, something like:

public static bool AlmostEquals
     (this double a, double b)
{
    return (Math.Abs(a - b) < 1e-5);
}

and then use it, when appropriate, like

MessageBox.Show((1.0 - 0.8).AlmostEquals(0.2));

Although if this is only a unit test, you might just add a method to your test module.

[IanWright83]

That is how things work, the only thing you can do is add a handy extension method to System.Double, something like:

public static bool AlmostEquals
     (this double a, double b)
{
    return (Math.Abs(a - b) < 1e-5);
}

and then use it, when appropriate, like

MessageBox.Show((1.0 - 0.8).AlmostEquals(0.2));

Although if this is only a unit test, you might just add a method to your test module.

Not sure off the top of my head, but is it possible to overload the double == operator in a similar approach using extension methods?

[vekipeki]

No, you cannot override the existing == operator (it is a static method). But I wouldn't call that a good idea even if it were possible, modifications like that would be a nightmare to debug.