#                  
## Overview
`Double.isNaN` property in Swift is used to check if an instance of type double is `NaN` (Not a Number).
## Syntax
```swift
Double.isNaN
```
## Parameter
This function does not take any parameters.
## Return value
The value returned is a boolean value. 
## Code example


// create some values
let d1 = 1.2
let d2 = 0.0
let d3 = Double.infinity * 0.0
let d4 = Double.infinity
let d5 = Double.nan * 2

// check if Not a Number
print(d1.isNaN)  // false
print(d2.isNaN)  // false 
print(d3.isNaN)  // true 
print(d4.isNaN)  // false
print(d5.isNaN)  // true

## Explanation
* **Lines 2-6**: We create some double values.
* **Lines 9-13**: We check to see if the values we created are `NaN` and print the results to the console.

What is Double.isNaN in Swift?

Double.isNaN checks if a double is NaN, returning a boolean. It takes no parameters.