Variadic Functions

Variadic functions can be called with any number of trailing arguments. For example, fmt.Println is a common variadic function.

package main

import "fmt"

// Here’s a function that will take an
// arbitrary number of ints as arguments.
func sum(nums ...int) {
    fmt.Print(nums, " ")
    total := 0

    // Within the function, the type of nums
    // is equivalent to []int. We can call len(nums)
    // iterate over it with range, etc.
    for _, num := range nums {
        total += num
    }
    fmt.Println(total)
}

func main() {

    // Variadic functions can be called in the usual way with individual arguments.
    sum(1, 2)
    sum(1, 2, 3)

    // If you already have multiple args in a slice
    // apply them to a variadic function using func(slice...) like this.
    nums := []int{1, 2, 3, 4}
    sum(nums...)
}

$ go run variadic-functions.go
[1 2] 3
[1 2 3] 6
[1 2 3 4] 10

Another key aspect of functions in Go is their ability to form closures, which we’ll look at next.