Table of Contents

Overview

In GO, the function is also a type. Two functions will be of the same type if

They have the same number of arguments with each argument is of the same type

They have the same number of return values and each return value is of the same type

Function as user-defined type can be declared using the type keyword like below. area is the name of the function of type func(int, int) int

type area func(int, int) int

Code

Example 1

In this example, we create a user-defined function type area. Then we create a variable of type area in the main function.

package main

import "fmt"

type area func(int, int) int

func main() {
    var areaF area = func(a, b int) int {
        return a * b
    }
    print(2, 3, areaF)
}

func print(x, y int, a area) {
    fmt.Printf("Area is: %d\n", a(x, y))
}

Output:

Example 2

In this example also we create a user-defined function type area. Then we create a function getAreaFunc() which returns the function of type area

package main

import "fmt"

type area func(int, int) int

func main() {
    areaF := getAreaFunc()
    print(2, 3, areaF)

}

func print(x, y int, a area) {
    fmt.Printf("Area is: %d\n", a(x, y))
}

func getAreaFunc() area {
    return func(x, y int) int {
        return x * y
    }
}

Output:

golang