Functions · Tuck

Functions are central in Go. We'll learn about them through a few examples.

package main

import "fmt"

This function takes two ints and returns their sum as an int. Parameter types come after the names, and the result type after the parameter list.

func plus(a int, b int) int {

Go requires explicit returns: it does not return the value of the last expression automatically.

	return a + b
}

Consecutive parameters of the same type can share one type name.

func plusPlus(a, b, c int) int {
	return a + b + c
}

Arguments are passed by value: the function gets a copy, so this does not change the caller's variable. Pointers (see Pointers) change that.

func reset(n int) {
	n = 0
}

func main() {

Call a function with name(args).

	res := plus(1, 2)
	fmt.Println("1+2 =", res)

	res = plusPlus(1, 2, 3)
	fmt.Println("1+2+3 =", res)

	n := 5
	reset(n)
	fmt.Println("still", n)

Functions are values too: they can be assigned and passed around.

	f := plus
	fmt.Printf("%T %d\n", f, f(10, 20))
}

$ go run ./12_functions
1+2 = 3
1+2+3 = 6
still 5
func(int, int) int 30