func functionname([parametername type]) [returntype] {

   //function body

}

//其中参数列列表和返回值列列表是可选

func functionname() {

   //function body

}

// 两数相加

// 三个整数相加简写：func add(a , b, c int) int{

func add(a int, b int) int {

	sum := a + b

	return sum

}

// 多返回值

// func calc(a, b int) (int, int){

func calc(a, b int) (sum int, sub int) {

	sum = a + b

	sub = a - b

	// sum := a + b

	// sub := a - b

	// return sum, sub

	//第二中写法

	return

}

// 多返回值

// func calc(a, b int) (int, int){

func calc(a, b int) (sum int, sub int) {

	sum = a + b

	sub = a - b

	// sum := a + b

	// sub := a - b

	// return sum, sub

	//第二中写法

	return

}

func main() {

    sum, sub := calc(200 ,100)

    fmt.Printf("%d %d", sum, sub)

}

func calc(a, b int) (int, int) {
  sum := a + b sub := a - b return sum, sub 
} 
func main() {
      sum, sub := add(2, 3)
 
} 

func calc(a, b int) (sum int, sub int) {

  sum = a + b sub = a - b return

}

func main() {

      sum, sub := add(2, 3)


}

func calc(a, b int) (sum int, sub int) {

  sum = a + b sub = a - b return

} 

func main() {

      sum, sub := add(2, 3)


}

func calc(a, b int) (sum int, sub int) {

  sum = a + b sub = a - b return

}

func main() {

      sum, _ := add(2, 3)


}

// 可变参数

func calc_v1(b ...int) int {

	sum := 0

	for i := 0; i < len(b); i++ {

		sum = sum + b[i]

	}

	return sum

}

// 固定参数和可变参数
func calc_v2(a int, b ...int) int {
   sum := a
   for i := 0; i < len(b); i++ {
      sum = sum + b[i]
   }
   return sum
}

// defer返回执行

// defer作用资源释放

func testDefer1() {

	defer fmt.Println("hello")

	defer fmt.Println("hello v2")

	defer fmt.Println("hello v3")

	fmt.Println("aaaaaa")

	fmt.Printf("bbbbbbbb")

}

/*

结果:

defer,后进先出，压栈

aaaaaaa

bbbbbbb

hello v3

hello v2

hello

*/

func testDefer2() {
   for i := 0; i < 5; i++ {
      defer fmt.Printf("i=%d\n", i)
   }

   fmt.Printf("running\n")
   fmt.Printf("reutrn:\n")
}

/*
runging
return
i=4
i=3
i=2
i=1
i=0
*/

// defer, 是预先定义的，只是return时返回结果
func testDefer3() {
   var i int = 0
   defer fmt.Printf("defer i=%d\n", i)
   i = 1000
   fmt.Println("i=%d\n", i)
}

/*
1000
defer i = 0
*/

package main

import "fmt"

func justify(n int) bool {

	if n <= 1 {

		return false

	}

	// 质数是除了他自己，不被任何数整除

	for i := 2; i < n; i++ {

		if n%i == 0 {

			return false

		}

	}

	return true

}

// 1-100的质数

func example1() {

	for i := 2; i < 100; i++ {

		if justify(i) == true {

			fmt.Printf("[%d] is prinme\n", i)

		}

	}

}

func is_shuixianhuashu(n int) bool {

	first := n % 10

	second := (n / 10) % 10

	third := (n / 100) % 10

	//fmt.Printf("first:%d second:%d third %d\n", n , first, second, third)

	sum := first*first*first + second*second*second + third*third*third

	if sum == n {

		return true

	}

	return false

}

// 水仙花束 x^3 + y^3 + z^3 = xyz

func example2() {

	for i := 2; i < 100; i++ {

		if is_shuixianhuashu(i) == true {

			fmt.Printf("[%d] is shuixianhuashu\n", i)

		}

	}

}

// 统计字符串中，字符，数字，空格，其他字符的个数

func calc(str string) (charCount int, numCount int, spaceCount int, otherCount int) {

	// 转为字符串utf-8

	utfChars := []rune(str)

	for i := 0; i < len(utfChars); i++ {

		if utfChars[i] >= 'a' && utfChars[i] <= 'z' || utfChars[i] >= 'A' && utfChars[i] <= 'z' {

			charCount++

			continue

		}

		if utfChars[i] >= '0' && utfChars[i] <= 9 {

			numCount++

			continue

		}

		if utfChars[i] >= ' ' {

			numCount++

			continue

		}

		otherCount++

	}

	return

}

func example3() {

	var str string = " dfsafa d范德萨 3984234"

	charCount, numCount, spCount, other := calc(str)

	fmt.Printf("charCount:%d, numCount:%d, spCount:%d, other:%d", charCount, numCount, spCount, other)

}

func main() {

	//example1()

	//example2()

	example3()

}