package main

import "fmt"

type User struct {
	Name string
	Age  int
}

func BirthdayValue(u User) { // copy
	u.Age++
}

func BirthdayPtr(u *User) { // mutate original
	u.Age++
}

func main() {
	u := User{Name: "M", Age: 20}

	BirthdayValue(u)
	fmt.Println("after value:", u.Age) // 20

	BirthdayPtr(&u)
	fmt.Println("after ptr:", u.Age) // 21
}

package main

type User struct{ Name string }

func NewUser(name string) *User {
	u := User{Name: name}
	return &u // u scope dışına çıkıyor -> genelde escape eder
}

func main() {
	_ = NewUser("M")
}

package main

import "fmt"

func makeCounter() func() int {
	x := 0
	return func() int {
		x++
		return x
	}
}

func main() {
	c := makeCounter()
	fmt.Println(c(), c(), c()) // 1 2 3
}

package main

import "fmt"

func main() {
	p := new(int)   // *int, zero value
	fmt.Println(*p) // 0

	// make: slice/map/channel initialize eder
	s := make([]int, 0, 10)
	m := make(map[string]int)
	ch := make(chan int, 1)

	fmt.Println(len(s), cap(s), m == nil, ch == nil)
}