package main

import (
	"fmt"
	"math"
)

//匿名函數
func main(){
	//無參匿名函數
	func(){
		fmt.Println("jonson")
	}()

	//有參匿名函數
	func(data int){
		fmt.Println("data:",data)
	}(5)

	//有返回值的匿名函數
	result:=func(data float64) float64{
		return math.Sqrt(data)
	}(9)

	fmt.Println("result:",result)

  //函數表達式
	greet:=func(){
		fmt.Println("greet jonson")
	}
	greet()

	fmt.Printf("greet的類型是%T\n",greet)

func greetjonson(){
	x:=0

	increment:= func() int{
		x++
		return x
	}

	fmt.Println(increment())
	fmt.Println(increment())
}

func makeGreeter() func() string{

	return func() string {
		return "hello jonson"
	}
}

func makeEvenGenerator() func() int{
	i:=0
	return func() int{
		i+=2
		return i
	}
}

func visit(numbers []int,callback func(int)){

	for _,n :=range numbers{
		callback(n)
	}
}

//  計算階乘     5   5*4*3*2*1

func factorial(x uint) uint{

	if x==0{
		return 1
	}
	return x * factorial(x-1)
}

// factorial(5)   //120
// returns: 5 * factorial(4)
// factorial(4)   /24
// 	returns: 4 * factorial(3)
// factorial(3)   //6
// 	returns: 3 * factorial(2)
// factorial(2)   //2
// 	returns: 2 * factorial(1)
// factorial(1)     //1
// 	returns: 1 * factorial(0)
// factorial(0)
// 	returns: 1

package main

import (
	"fmt"
	"math"
)

//匿名函數
func main(){
	//無參匿名函數
	func(){
		fmt.Println("jonson")
	}()

	//有參匿名函數
	func(data int){
		fmt.Println("data:",data)
	}(5)

	//有返回值的匿名函數
	result:=func(data float64) float64{
		return math.Sqrt(data)
	}(9)

	fmt.Println("result:",result)


	greet:=func(){
		fmt.Println("greet jonson")
	}
	greet()

	fmt.Printf("greet的類型是%T\n",greet)

	//閉包
	greetjonson()

	//函數作為返回值

	  makejonson := makeGreeter()

	  fmt.Printf("類型：%T，返回值：%v\n",makejonson,makejonson())



	//閉包做為返回值
	makeeven := makeEvenGenerator()

	fmt.Println("makeeven i = ",makeeven())
	fmt.Println("makeeven i = ",makeeven())
	fmt.Println("makeeven i = ",makeeven())

	//callback函數作為參數
	visit([]int{1,2,3,4},func(n int){
		fmt.Println(n+1)
	})

	//死循環
	fmt.Println(factorial(5))


	var i uint = 0
	for ;i<20;i++{

		fmt.Println(fabicc(i))

	}
}

//閉包


func greetjonson(){
	x:=0

	increment:= func() int{
		x++
		return x
	}

	fmt.Println(increment())
	fmt.Println(increment())
}
//函數作為返回值

func makeGreeter() func() string{

	return func() string {
		return "hello jonson"
	}
}


//閉包與函數返回值

func makeEvenGenerator() func() int{
	i:=0
	return func() int{
		i+=2
		return i
	}
}


//callback函數作為參數

func visit(numbers []int,callback func(int)){

	for _,n :=range numbers{
		callback(n)
	}
}


//遞歸

//  計算階乘     5   5*4*3*2*1

func factorial(x uint) uint{

	if x==0{
		return 1
	}
	return x * factorial(x-1)
}

//fabicc


func fabicc(x  uint) uint{

	if(x==0){
		return 0
	}
	if(x==1){
		return 1
	}

	return fabicc(x-2) + fabicc(x-1)
}