Summary - Functions

Use multiple return and variadic parameters to write a helper.

Functions summary

In this group you learned the func name(parameters) result syntax, pass by value, multiple returns like (result, error), named returns, variadic parameters with ..., anonymous functions and closures.

func uygula(s []int, f func(int) int) []int {
    sonuc := make([]int, len(s))
    for i, v := range s {
        sonuc[i] = f(v)
    }
    return sonuc
}

Functions that take functions (higher-order) gather repeated loops in one place.

defer

defer postpones a call until the function ends; several defers run in reverse order (last in, first out). It's used for cleanup such as closing files and unlocking:

func islem() {
    defer fmt.Println("bitti")
    fmt.Println("çalışıyor")
}
// çalışıyor
// bitti

A defer's arguments are evaluated when the defer line runs; the call itself happens at the end.

Exercise Higher-order function

Write the uygula function above. Print the result of uygula([]int{1, 2, 3}, func(n int) int { return n * n }).

Show example solution

package main

import "fmt"

func uygula(s []int, f func(int) int) []int {
    sonuc := make([]int, len(s))
    for i, v := range s {
        sonuc[i] = f(v)
    }
    return sonuc
}

func main() {
    fmt.Println(uygula([]int{1, 2, 3}, func(n int) int { return n * n }))
}

Test yourself

What does <code>uygula([]int{1, 2}, func(n int) int { return n + 10 })</code> return?
- [11 12]
- [1 2]
- 23
- [10 10]
Show answer

[11 12] — uygula applies the given function to every element: 1+10, 2+10.

Postpone

func oku() {
    ____ fmt.Println("dosya kapandı")
    fmt.Println("okunuyor")
}

Show answer

func oku() {
    defer fmt.Println("dosya kapandı")
    fmt.Println("okunuyor")
}

Group summary

func ...

Definition
(int, error)

Multiple returns
...int

Variadic
defer

Postponing to the end

Next lesson: if, else if, else

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