Explain What is half-open range operator?

Half-Open Range Operator: It is an operator (a<b) that is used to defines a range that runs from a to b but it doesn’t contain b. The reason for its name that is half-open is that it does not contains its last value, just have its first value. The value of 'a' compulsory is not greater than b in the closed ranged operator. The resulting range will be empty in the case of a is equal to b.

It is useful when you are working with zero-based lists like arrays where it is useful to calculate the length of the list. For example:

let names = ["Alley", "Anna", "Jack", "Brian"]
let count = names.count
for i in 0..<count span id="docs-internal-guid-b356581b-7fff-3109-a868-e60b14559aae">count
print("Person \(i + 1) is called \(names[i])")
} // Person 1 is called Alley, Person 2 is called Anna, Person 3 is called Jack, Person 4 is called Brian