# Golang Odd and Even Numbers

Use modulo division to decide whether a number is even or odd. Some sample numbers are tested.**Odd, even numbers.** Some numbers are odd. Others are even. We can use modulo division to tell whether a number is divisible by two. This tells us the parity of a number.

**An odd issue.** To tell if a number is even, we see if it evenly divisible by 2. But to tell if it is odd, we must allow a remainder of either 1 or -1. A negative number may be odd.

**Example program.** This program introduces the Even and Odd funcs. We test Even() and Odd() in the main method. Both methods return a bool.

**Even:** We use modulo division to see if a number is evenly divisible by 2. If there is no remainder, we have an even number.

**Odd:** We implement Odd() in terms of Even. Every integer that is not Even is Odd.

**Result:** The program iterates through the numbers -4 through 4 inclusive and displays whether each one is even or not.

**Golang program that test seven, odd numbers**
package main
import "fmt"
func __Even__(number int) bool {
return *number%2 == 0*
}
func __Odd__(number int) bool {*
// Odd should return not even.
// ... We cannot check for 1 remainder.
// ... That fails for negative numbers.
*return !Even(number)
}
func main() {
for i := -4; i <= 4; i++ {*
// Test the even func.
*fmt.Printf("Number: %v, Even: %v", i, __Even__(i))
fmt.Println()
}*
// Test the odd method.
*if __Odd__(1) {
fmt.Println("ok")
}
}
**Output**
Number: -4, Even: true
Number: -3, Even: false
Number: -2, Even: true
Number: -1, Even: false
Number: 0, Even: true
Number: 1, Even: false
Number: 2, Even: true
Number: 3, Even: false
Number: 4, Even: true
ok

**Simple methods.** In the math package, I found no methods that reveal the parity of numbers. So a simple method that tells us this can be useful in quick Go programs.

Math: golang.org**In general,** using built-in methods from the "math" package is the best choice. So it is worthwhile to check that no existing math methods are available.

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