Range

You create a Range instance by using the half-open range operator (..<).

let underFive = 0.0..<5.0

You can use a Range instance to quickly check if a value is contained in a particular range of values. For example:

underFive.contains(3.14)
// true
underFive.contains(6.28)
// false
underFive.contains(5.0)
// false

Range instances can represent an empty interval, unlike ClosedRange.

let empty = 0.0..<0.0
empty.contains(0.0)
// false
empty.isEmpty
// true

Using a Range as a Collection of Consecutive Values

When a range uses integers as its lower and upper bounds, or any other type that conforms to the Strideable protocol with an integer stride, you can use that range in a for-in loop or with any sequence or collection method. The elements of the range are the consecutive values from its lower bound up to, but not including, its upper bound.

for n in 3..<5 {
    print(n)
}
// Prints "3"
// Prints "4"

Because floating-point types such as Float and Double are their own Stride types, they cannot be used as the bounds of a countable range. If you need to iterate over consecutive floating-point values, see the stride(from:to:by:) function.