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Higher-Order Functions

Higher-Order Functions

This lesson discusses how to use functions as parameters and values.

We'll cover the following...

Function used as a value

Functions can be used as values just like any other value in Go. In the following code, f1 is assigned a value, the function inc1:

func inc1(x int) int { return x+1 }
f1 := inc1 // f1 := func (x int) int { return x+1 }

Function used as a parameter

Functions can be used as parameters in another function. The passed function can then be called within the body of that function; that is why it is commonly called a callback. To illustrate, here is a simple example:

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package main
import (
    "fmt"
)
func main() {
    callback(1, Add) // function passed as a parameter
}
func Add(a, b int) {
    fmt.Printf("The sum of %d and %d is: %d\n", a, b, a + b)
}
func callback(y int, f func(int, int)) {
    f(y, 2) // this becomes Add(1, 2)
}

To understand the code, look at line 10 at the function header of the function Add. It takes two parameters a and b and prints the sum of the parameters. In the main, we are just calling the callback function as: callback(1, Add). Here, we have two parameters: the first is ...