The following lines declare a myFunction variable with a function type—specifically, a function that receives an Int argument and returns a Bool value. The variable works in the same way as an argument that specifies a function type for a function:
var myFunction: (Int -> Bool)
myFunction = divisibleBy5
let myNumber = 20
print("Is \(myNumber) divisible by 5: \(myFunction(myNumber))")Then, the code assigns the divisibleBy5 function to myFunction. It is very important to understand that the line doesn't call the divisibleBy5 function and save the result of this call in the myFunction variable. Instead, it just assigns the function to the variable that has a function type. The lack of a parenthesis after the function name makes the difference.
Then, the code prints whether the Int value specified in the myNumber constant is divisible by 5 or not using the myFunction variable to call the referenced function with myNumber as an argument.
The following...
