Variadic functions

Learn to take a variable number of arguments with the ... operator.

Variadic functions

If ... is written before the type of the last parameter, the function takes any number of arguments of that type; inside, they appear as a slice:

func topla(sayilar ...int) int {
    t := 0
    for _, n := range sayilar {
        t += n
    }
    return t
}

fmt.Println(topla(1, 2, 3))  // 6
fmt.Println(topla())         // 0

fmt.Println is a variadic function too.

Rules

The variadic parameter can only be the last parameter: func yaz(onEk string, degerler ...int). With no arguments, the slice is nil and its len is zero. append(s, other...) uses the same spread syntax.

Exercise Average

Write ortalama(sayilar ...float64) float64; return 0 if there are no arguments. Print the result of ortalama(2, 4, 9).

Show example solution

package main

import "fmt"

func ortalama(sayilar ...float64) float64 {
    if len(sayilar) == 0 {
        return 0
    }
    t := 0.0
    for _, n := range sayilar {
        t += n
    }
    return t / float64(len(sayilar))
}

func main() {
    fmt.Println(ortalama(2, 4, 9))
}

Test yourself

How do you pass a slice you have to a variadic function?
- topla(...liste)
- topla(*liste)
- topla(liste...)
- topla(liste)
Show answer

topla(liste...) — Writing ... after the slice spreads it into individual arguments; writing just liste is a type error.

Spread the slice

liste := []int{4, 5, 6}
fmt.Println(topla(liste____))

Show answer

liste := []int{4, 5, 6}
fmt.Println(topla(liste...))

Call and result

topla(1, 2, 3)

6
topla()

0
topla([]int{4, 5}...)

9
topla(10)

10

Next lesson: Anonymous functions

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