Ranges

Published Nov 27, 2023
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Ranges are used to create an interval of values. There are two kinds of range structures, Range for creating half-open ranges and ClosedRange for creating closed ranges.

Creating Ranges

Half-open Ranges

Range instances are declared using the ..< half-open range operator. They include values from a lower bound up to, but excluding an upper bound.

The syntax below shows how to create a half-open range with lower as the lower bound value and upper as the upper bound value:

let newRange = lower..<upper

Closed Ranges

ClosedRange instances are declared using the ... closed range operator. They contain values from a lower bound up to and including an upper bound.

The syntax below shows how to create a closed range with lower as the lower bound value and upper as the upper bound value:

let newClosedRange = lower...upper

Using Ranges

Some useful applications of ranges are:

  • For iteration with for-in loops.
  • In switch statements to find out if a value lies within an interval.
  • Selecting a section of an array.

For-in Loop Example

The example below uses for-in loops with a half-open range and then a closed range to print some emoji trees:

for n in 1..<4 {
print(String(repeating: "šŸŒ²", count: n))
}
for n in 1...4 {
print(String(repeating: "šŸŒ³", count: n))
}

The above example will result in the following output:

šŸŒ²
šŸŒ²šŸŒ²
šŸŒ²šŸŒ²šŸŒ²
šŸŒ³
šŸŒ³šŸŒ³
šŸŒ³šŸŒ³šŸŒ³
šŸŒ³šŸŒ³šŸŒ³šŸŒ³

Switch Example

The example below uses a switch statement and a closed range to determine which emoji to print depending on the value of treeHeight:

let treeHeight = 2
switch treeHeight {
case 0...30:
print("šŸŒ±")
default:
print("šŸŒ³")
}

The above example will result in the following output:

šŸŒ±

Array Example

The example below prints out a section of the tree array using a closed range to select the element indexes:

let trees = ["Pine", "Oak", "Ash", "Willow", "Olive"]
print(trees[2...4])

The above example will result in the following output:

["Ash", "Willow", "Olive"]

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