What are one-sided ranges in Swift?
We can use one-sided ranges to create a range without upper or lower bound values.
Syntax
a...
This will include everything from the lower bound a.
...a
This will include everything before the upper bound a. a is included in the range.
..<a
This will include everything before the upper bound a. a is excluded in the range.
Example for one-sided range a...
let numbers = 1...print(numbers);print(numbers.contains(1))print(numbers.contains(1000000000))
In the code above, we created a one-sided range 1.... This range will contain every value from 1.
Example for one-sided range ...a
let numbers = ...10print(numbers);print(numbers.contains(-1))print(numbers.contains(10))print(numbers.contains(-1000000000))
In the code above, we created a one-sided range ...10. This range will contain every value before 10 (10 is included in the range).
Example for one-sided range ..<a
let numbers = ..<1print(numbers);print(numbers.contains(-1000000000))print(numbers.contains(1)) // false
In the code above, we created a one-sided range ..<1. This range will contain every value before 1 (1 is excluded from the range). After that, we checked if 1 is present in the range. This will return false.
One-sided range in a real example
let fruits = ["apple", "grapes", "banana", "water melon", "guava"]print(fruits[1...]) // Print all items from index 1print(fruits[...2]) // Prints all items upto 2nd index, 2nd index element also includedprint(fruits[..<2]) // Prints all items upto 2nd index, 2nd index element is not inclulded
In the code above, we used the following to slice the array.
-
fruits[1...]: This will return all the array values from index 1. -
fruits[...2]: This will return all the array values before index 2; the value at index 2 is also included. -
fruits[..<2]: This will return all the array values before index 2; the value at index 2 is not included.
