Swift - Range Operators

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Swift provides range operators, such as a..<b and a...b that can be used as a shortcut for expressing a range of values. These operators are generally used with a for-in loop. There are three types of range operators are available in Swift:

1. Closed Range Operator

A closed range operator is used to define a range that contains both starting and end values. In other words, a closed range is used to create a range from x to y, including the value of x and y. Here the starting value or value of x must not be greater than the ending value or value of y.

Syntax

Following is the syntax of the closed range operator −

xy

Example

Swift program to display a sequence of numbers using a closed range operator.

import Foundation

// For loop to display a sequence of numbers
for x in 3...11{
   print(x)
}

The output of the above example is:

3
4
5
6
7
8
9
10
11

2. Half-Open Range Operator

A half-open range operator is used to create a range from x to y. This range only includes the starting value and does not include the ending value or y. Also, the value of x or the starting value should not be greater than the ending value of y.

Or if the value of x is equal to y, then the range will be empty. This operator is generally used with zero-based lists like arrays, etc.

Syntax

Following is the syntax of the half-open range operator −

x..<y

Example

Swift program to display the elements of an array using a half-open range operator.

import Foundation

let arr = [1, 4, 6, 2, 7]
for x in 0..<arr.count{
	print(arr[x])
}

The output of the above example is:

1
4
6
2
7

3. One-Sided Ranges

The one-sided ranges are used to define ranges that have a value of only one side. Such types of ranges are used when we need to know from where the iteration should begin. One-sided ranges are of two types −

• Partial Range from Start − It defines a range that starts from the beginning of the given collection or sequence and goes to the specified end value. This range contains only the end value and does not contain the starting value.

Syntax

Following is the syntax of partial range from start −

x or ..<x

• Partial Range to the End − It creates a range that starts from the specified value and goes all the way to the end of the given collection or sequence. This range contains only the starting value and does not contain the end value.

Syntax

Following is the syntax of partial range to the end −

x

Example

Swift program to demonstrate partial range to the start.

import Foundation

let arr = [1, 4, 6, 2, 7]

// This one-sided range displays elements till index 3
print("Sequence 1:")
for x in arr[...3]{
   print(x)
}

// This one-sided range displays all the elements before index 3
print("Sequence 2:")
for y in arr[..<3]{
   print(y)
}

The output of the above example is:

Sequence 1:
1
4
6
2
Sequence 2:
1
4
6

Example

Swift program to demonstrate partial range to the end.

import Foundation

let arr = [1, 4, 6, 2, 7]

// This one-sided range displays all elements 
// starting from index 2 to the end of the sequence 
print("Sequence:")
for x in arr[2...]{
   print(x)
}

The output of the above example is:

Sequence:
6
2
7

Access Array Elements Using Swift Range Operators

The range operators can be used to access array elements. You can use these operators inside the square brackets [] with the array name to access the particular range of the elements.

The syntax to access array elements using range operator is:

array_name [lower_bound...upper_bound]

Example

Swift program to access array elements using range operators.

import Foundation

// Array of names
let names = ["Aarav", "Diya", "Kabir", "Meera", "Vivaan", "Anaya", "Ishaan"]

// Accessing a range of elements using closed range operator
let selectedNames = names[1...4]

for name in selectedNames {
    print(name)
}

The output of the above example is:

Diya
Kabir
Meera
Vivaan

Important Points to Remember

Remember these important points while working with range operators:

• The lower bound value must be less than or equal to the upper bound when using a closed range (e.g., 1...5).
• Range operators work with both positive and negative values, but they do not reverse the order of iteration. If the lower bound is greater than the upper bound, the range will be invalid and result in a runtime error.