What is the Swift equivalent of isnan ()?

Question

What is equivalent to isnan() in Swift? I need to check if some operation results are valid and remove those invalid like x / 0 Thanks

Answer 1

It is defined in the protocol FloatingPointNumber , which both Float and Double match. The following is used:

 let d = 3.0 let isNan = d.isNaN // False let d = Double.NaN let isNan = d.isNaN // True 

If you are looking for a way to do this check yourself, you can. IEEE determines that NaN! = NaN, that is, you cannot directly compare NaN with a number to determine its value-number. However, you can verify that maybeNaN != maybeNaN . If this condition evaluates to true, you are dealing with NaN.

Although you need to use aVariable.isNaN to determine if the value is NaN.

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As a quick note, if you are less sure about the classification of the value you are working with, you can switch the value of your FloatingPointNumber corresponding floatingPointClass type.

 let noClueWhatThisIs: Double = // ... switch noClueWhatThisIs.floatingPointClass { case .SignalingNaN: print(FloatingPointClassification.SignalingNaN) case .QuietNaN: print(FloatingPointClassification.QuietNaN) case .NegativeInfinity: print(FloatingPointClassification.NegativeInfinity) case .NegativeNormal: print(FloatingPointClassification.NegativeNormal) case .NegativeSubnormal: print(FloatingPointClassification.NegativeSubnormal) case .NegativeZero: print(FloatingPointClassification.NegativeZero) case .PositiveZero: print(FloatingPointClassification.PositiveZero) case .PositiveSubnormal: print(FloatingPointClassification.PositiveSubnormal) case .PositiveNormal: print(FloatingPointClassification.PositiveNormal) case .PositiveInfinity: print(FloatingPointClassification.PositiveInfinity) } 

Its values ​​are declared in the FloatingPointClassification listing.

Answer 2

The accepted answer works, but when I first saw it, I did not quite understand because of the example.

Here is an example from Apple for those who are not clear:

 let x = 0.0 let y = x * .infinity // y is a NaN if y.isNan { print("this is NaN") // this will print } else { print("this isn't Nan") }