Go-控制语句那些事

Go-控制语句那些事

for range 循环的副本switch 中的 case 语句常量(表达式值)不可以重复

上代码, 自己品

package main

import "fmt"

func main() {
	list := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
	for i := range list {
		if i == 3 {
			list[i] |= i
		}
	}

	fmt.Println(list) // [1 2 3 7 5 6 7 8 9]
}

package main

import "fmt"

func main() {
	list := [...]int{1, 2, 3, 4, 5, 6, 7, 8, 9} // 数组
	maxIndex := len(list) - 1
	for i, ele := range list { // 循环的是数组的副本, ele是副本的
		fmt.Println(list[i], ele)
		if i == maxIndex {
			list[0] += ele
		} else {
			list[i+1] += ele
		}
	}

	fmt.Println(list) // [10 3 5 7 9 11 13 15 17]
}

package main

import "fmt"

func main() {
	list := []int{1, 2, 3, 4, 5, 6, 7, 8, 9} // 切片
	maxIndex := len(list) - 1
	for i, ele := range list { // 循环的是切片的副本, 切面是引用类型, 所以是指针的副本, ele是最新的
		fmt.Println(list[i], ele)
		if i == maxIndex {
			list[0] += ele
		} else {
			list[i+1] += ele
		}
	}

	fmt.Println(list) // [46 3 6 10 15 21 28 36 45]
}

package main

import "fmt"

func main() {
	list := [...]int{1, 2, 3, 4, 5, 6, 7, 8, 9} // 数组
	//list := []int{1, 2, 3, 4, 5, 6, 7, 8, 9} // 切片
	switch 1 + 3 {
	case list[0], list[1]:
		fmt.Println("0 or 1")
	case list[2], list[3]:
		fmt.Println("2 or 3")
	case list[4], list[5]:
		fmt.Println("4 or 5")
	}

	//	2 or 3
}

package main

import "fmt"

func main() {
	list := [...]int8{1, 2, 3, 4, 5, 6, 7, 8, 9} // 数组
	//list := []int{1, 2, 3, 4, 5, 6, 7, 8, 9} // 切片
	switch 2 { // int
	case list[0]: // in8, 编译错误: invalid case list[0] in switch on 2 (mismatched types int8 and int)
		fmt.Println("0")
	case list[1]:
		fmt.Println("1")
	case list[2]:
		fmt.Println("2")
	}

	//编译错误
}

package main

import "fmt"

func main() {
	list := [...]int8{1, 2, 3, 4, 5, 6, 7, 8, 9} // 数组
	//list := []int{1, 2, 3, 4, 5, 6, 7, 8, 9} // 切片
	switch list[0] { // int8
	case 0: // int, 会转换成 int8
		fmt.Println("0")
	case 1:
		fmt.Println("1")
	case 2:
		fmt.Println("2")
	}

	// 1
}

package main

import "fmt"

func main() {
	list := [...]int8{1, 2, 3, 4, 5, 6, 7, 8, 9} // 数组
	//list := []int{1, 2, 3, 4, 5, 6, 7, 8, 9} // 切片
	switch list[0] { // int8
	case 0:
		fmt.Println("0")
	case 1:
		fmt.Println("1")
	case 2:
		fmt.Println("2")
	case 0: //编译错误: duplicate case 0 in switch. case语句表达式的结果值不能重复. 只有常量才会
		fmt.Println("0(2)")
	case 5 - 5: //编译错误: duplicate case 5 - 5 (value 0) in switch
		fmt.Println("0(5-5)")
	}
}

package main

import "fmt"

func main() {
	list := [...]int8{1, 2, 3, 4, 5, 6, 7, 8, 9} // 数组
	//list := []int{1, 2, 3, 4, 5, 6, 7, 8, 9} // 切片
	switch list[0] { // int8
	case list[0]: // int, 会转换成 int8
		fmt.Println("0")
	case list[1]:
		fmt.Println("1")
	case list[0], list[2]:
		fmt.Println("2")
	case list[0]:
		fmt.Println("0")
	}

	// 0
}

package main

import "fmt"

func main() {
	list := interface{}(byte(127))
	switch t := list.(type) {
	case uint8, uint16:
		fmt.Println("uint8 or uint16")
	case byte: // 编译错误duplicate case byte in type switch. type byte = uint8
		fmt.Println("byte")
	default:
		fmt.Println("未知类型", t)
	}
}