Unlike for and while loops, which test the loop condition at the top of the loop, the repeat…while loop checks its condition at the bottom of the loop. A repeat…while loop is similar to a while loop, except that a repeat…while loop is guaranteed to execute at least once before checking the loop condition.

Syntax

The syntax of a repeat…while loop −

repeat{
   statement(s);
} while( condition );

It should be noted that the conditional expression appears at the end of the loop, so the statement(s) in the loop execute once before the condition is tested. If the condition is true, the control flow jumps back up to repeat, and the statement(s) in the loop execute again. This process repeats until the given condition becomes false.

Flow Diagram

The following flow diagram will show how the repeat-while loop works −

Example

Swift program to demonstrate the use of repeat while loop.

import Foundation

var index = 10

repeat {
   print( "Value of index is (index)")
   index = index + 1
} while index < 20 

Output

It will produce the following output −

Value of index is 10
Value of index is 11
Value of index is 12
Value of index is 13
Value of index is 14
Value of index is 15
Value of index is 16
Value of index is 17
Value of index is 18
Value of index is 19

Example

Swift program to find the sum of numbers from 1 to 10 using repeat while loop.

import Foundation
var sum = 0
var num = 1
repeat {
   sum += num
   num += 1
} while num <= 10
print("Sum of numbers from 1 to 10 is: (sum)")

Output

It will produce the following output −

Sum of numbers from 1 to 10 is: 55