How to test for a NaN

ustk

I am trying to test if a number is NaN after some derivative computation...

I can throw an assertion in the console, but I'd like to be able to detect the NaN in code so I can force it, let's say to 0.0 instead.

When I simply print the number, I get "nan" in the console.
But I can't seem to detect it in script:

Console.print(myNumber); // nan

if (myNumber == "nan") // fails to detect
    myNumber = 0.0;

if (myNumber == NaN) // also fails to detect
    myNumber = 0.0;

Though if I do:

// force NaN
myNumber = NaN;

if (myNumber == NaN) // This "forced" NaN is detected
    myNumber = 0.0;

So why this difference between two NaNs? Is one with cheese while the other is raw?

Matt_SF

@ustk I'm not in front of my computer and I might be talking nonsense but, since you're looking for 'NotANumber', what if you test it like this? :

if(yourNumber! = typeof(number))

d.healey

@Matt_SF

Don't even need the parentheses

if (typeof valueToTest != "number")

Matt_SF

@d-healey ah, good to know!

ustk

@d-healey @Matt_SF thanks both, but I should have mentioned that when the value is computed and throws a nan in the console, then the variable typeof is still evaluated as number which is probably a bug.

The nan from computed value is different than a NaN manually forced. I'll put a snippet together tomorrow to demonstrate the issue...

@Christoph-Hart, anything about this?

ustk

So here's a little snippet

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Also, as strange as it sounds, a NaN is of type number so checking for this always returns true. There should be a way to just check for val == NaN instead

Matt_SF

@ustk

HiseSnippet 999.3ocsVstiaTCE1SxNHlgKhJwCvg7GRT2lMAJEDUao6lKn.cyF0Tp5+pb73zwjI1Q1dRHhceQ3oj2.33YlMYRSJfhnSjhlyU+cN93OOizJF2XTZhWvKVufS79X+wqk13NwTgjLnKw6S8uhZrbMjq5x0KnFCOh34U8GcJ7BNgj87m+vkzDpjw2phPdoRv3OSLWX2pczS+YQRReZD+Eh4k79gOc.SI6nRToHdp52hrfxlQeCeH04VEeh2GzKRXU5wVpkaHdmboJZ83X0JYt+uTXDSR3Ng1jwXhxU2WkD4PrSKoSrHIZzc0sgfYYz1tP07tvm6ekHRrQ+1twmkY.1FQ49gWkcgW0cfW6xvqUI3c.H4UBRmjCo64OloEKras3vyG4OPhaNSoXauLTx8kT4Op52QgdHsMmSmw6qQgMQT+QsZcJf+03wgnWFUBuIKgS00QEggmcFXi0pUFfBRpDDSgETMcNbNzJTHSDRNLMUxrBkDh3ZwRpUrjWm1H72CCzbapVBsgG.WQswMYJSLZBNKWzHjYh2GZeF8wg2hqWHKlyl0WoGRGVuT9Z0HCNu8JV16kzjrEEgn6c37ygZHjqA2bSPP.fUhIVklDAS3XMwgUz0gAAVrwplBEAf4w4tyYFU9kVmuoX6DPnxxCy4hKHPX.Y57Ib8ofvt0czdylM2KyoxH9TD6QMbI+WSMVvpxw+ovjTKXvAbfh84Ipk7S2rT3pfIIaAyWMfJWmAcrTCtaGagVHs0q8DnK2xyaMitX73dcqgssfaCC3IF999+Ek7u+ECdVg+Ag6mXGB9dnFtWUpttOp3F2aoE1vYCCGmsx1Lbox8Cq2epndwcfUXoQstV1JkdlAVEykvTklIjuAGxvZNLHQwvrOesqAjsojkI2FagtLkM1ufB5e8y6zqK7fmTp9uMby7hRNTY4WKqmMofVf21zzoGzl6.jVkjv0GzriDS+OEX86FUxZVabDOYuKcg+6ltnLaFK+7bIGUxARg85Eb46hiiTPBfu8KC5RsTGGSgNzuEbsU3ffWW9RjvNmwIvuK2LypVfT16QGgDgpnzDpcW1Q2UBEFvdvNTRNZGoQXWW9Ji+2nL+uBw64ORXYwGFiUN.FwN06CLVbQym32a5T7T3V.dhe+W894VExyUoV7jFx+pE+FNuMLc9X7tVFGWcoDoIPcdUbSK4xsbxtNvXtLJS3uvmBiscxdEFaemQxbJSqdMKex2cU1GloAwjL6V7.7yIPYnMI6zP497b7l0WyX6lp8B7qN1.+5iMvGdrA9MGafO5XC7aO1.+t+8.ce3yEoV077iMDxUi5kQk340SRwIvroUxeS8x1Nb

if (val == "nan")

Seems to work :)

d.healey

Why not avoid the nan at the source?

inline function derivative(a)
{
	return a == 0 ? -1 : 1 - Math.cosh(a) / Math.sinh(a) + 1/a;
}

ustk

@Matt_SF Oh nice! I was certain I tested this too but apparently not!

@d-healey Yeah the apparence I could just treat it this way but unfortunately the number I need to return in the case of a NaN is depending on the context, so it's not that simple i the end

How to test for a NaN

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