Odd, even. The parity of a number is sometimes important. 0 is even. 1 is odd. With odd and even checks, we can alternate a test or computation in a loop.
With modulo division in Swift, we can tell the parity of a number. If a modulo division by 2 returns 0, we have an even number. If it does not, we have an odd.
Even. Let us begin with the even() func. This returns a bool indicating whether the number is even. It returns the result of an expression—whether the number is evenly divisible by 2.
Start We use a for-loop over the numbers 0 through 5 inclusive. We test whether these numbers are even and print the results.
Note Negative numbers are correctly supported here. A negative number can be evenly divisible by 2.
func even(number: Int) -> Bool {
// Return true if number is evenly divisible by 2.
return number % 2 == 0
}
// Test the parity of these numbers.
for i in 0...5 {
let result = even(number: i)
// Display result.
print("\(i) = \(result)")
}0 = true
1 = false
2 = true
3 = false
4 = true
5 = false
Odd. An odd number is not even. It can be negative. Here we test for "not equal to zero." We do not test for a remainder of 1, as this would not support negative numbers.
func odd(number: Int) -> Bool {
// Divide number by 2.// ... If remainder is 1, we have a positive odd number.// ... If remainder is -1, it is odd and negative.// ... Same as "not even."
return number % 2 != 0
}
for i in -3...3 {
let result = odd(number: i)
print("\(i) = \(result)")
}-3 = true
-2 = false
-1 = true
0 = false
1 = true
2 = false
3 = true
Summary. Usually the parity of a number is not directly needed. But with even() and odd() we can test for even numbers and odd ones to change how we handle values in a loop.
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This page was last updated on Aug 22, 2023 (edit).