finger :=6
fmt.Printf("Finger %d is ", finger)switch finger {
case1:
fmt.Println("Thumb")case2:
fmt.Println("Index")case3:
fmt.Println("Middle")case4:// 不能出现相同的数字
fmt.Println("Ring")case5:
fmt.Println("Pinky")default://default case 如果没有则执行默认
fmt.Println("incorrect finger number")}/// 输出: Finger 6 is incorrect finger number
2. Multiple expressions in case
letter :="a"
fmt.Printf("Letter %s is a ", letter)switch letter {
case"a","b","c","d":
fmt.Println("Vowel")default:
fmt.Println("No Vowel")}/// 输出 Letter a is a Vowel
3. Expressionless switch
num :=75switch{
// expression is omittedcase num >=0&& num <=50:
fmt.Printf("%d is greater than 0 and less than 50", num)case num >=51&& num <=100:
fmt.Printf("%d is greater than 51 and less than 100", num)case num >=101:
fmt.Printf("%d is greater than 100", num)}/// 75 is greater than 51 and less than 100
4. Fallthrough
switch num :=25;{
case num <50:
fmt.Printf("%d is lesser than 50\n", num)fallthrough// 关键字case num >100:// 当这句是错误的 也会继续运行下一句
fmt.Printf("%d is greater than 100\n", num)}/// 25 is lesser than 50/// 25 is greater than 100
5. break
switch num :=-7;{
case num <50:if num <0{
break// 小于0就被break了}
fmt.Printf("%d is lesser than 50\n", num)fallthroughcase num <100:
fmt.Printf("%d is lesser than 100\n", num)fallthroughcase num <200:
fmt.Printf("%d is lesser than 200", num)}
6. break for loop
randloop:for{
switch i := rand.Intn(100);{
// 100以内随机数case i%2==0:// 能被2整除的i
fmt.Printf("Generated even number %d", i)break randloop // 必须添加break}}/// Generated even number 86
二. Arrays数组
var a [3]int// int array with length 3
a[0]=11
a[1]=12
a[2]=13
b :=[3]int{
15,16,17}// 注意声明了int类型就不能是别的类型
c :=[3]int{
18}
d :=[...]int{
19,20,21}
e :=[...]string{
"USA","China","India","Germany","France"}
f := e // a copy of e is assigned to f
f[0]="Singapore"
fmt.Println("a is ", a)
fmt.Println("b is ", b)
fmt.Println(b)// [15 16 17]
fmt.Println(a)// [11 12 13]
fmt.Println(c)// [18 0 0]
fmt.Println(d)// [19 20 21]
fmt.Println(e)// [USA China India Germany France]
fmt.Println(f)// [Singapore China India Germany France]
fmt.Println(len(f))// 5 Length of an array
1. when arrays are passed to functions as parameters
package main
import"fmt"funcchangeLocal(num [5]int){
num[0]=22
fmt.Println("inside function ", num)}funcmain(){
num :=[...]int{
33,44,55,66,77}
fmt.Println("bebore passing to function", num)changeLocal(num)// num is passing by value
fmt.Println("after passing to function", num)}// bebore passing to function [33 44 55 66 77]// inside function [22 44 55 66 77]// after passing to function [33 44 55 66 77]
2. Iterating arrays using range
a :=[...]float64{
13.14,14.13,15.20,21,52}for i :=0; i <len(a); i++{
fmt.Printf("%d th element of a is %.2f\n", i, a[i])}// 0 th element of a is 13.14// 1 th element of a is 14.13// 2 th element of a is 15.20// 3 th element of a is 21.00// 4 th element of a is 52.00
a :=[...]float64{
13.14,14.13,15.20,21,52}
sum :=float64(0)for i, v :=range a {
//range returns both the index and value
fmt.Printf("%d the element of a is %.2f\n", i, v)
sum += v
}
fmt.Println("\nsum of all elements of a", sum)// 0 the element of a is 13.14// 1 the element of a is 14.13// 2 the element of a is 15.20// 3 the element of a is 21.00// 4 the element of a is 52.00// sum of all elements of a 115.47
3.Multidimensional arrays 多维数组
a :=[...]float64{
13.14,14.13,15.20,21,52}for i :=0; i <len(a); i++{
fmt.Printf("%d th element of a is %.2f\n", i, a[i])}// 0 th element of a is 13.14// 1 th element of a is 14.13// 2 th element of a is 15.20// 3 th element of a is 21.00// 4 th element of a is 52.00
a :=[...]float64{
13.14,14.13,15.20,21,52}
sum :=float64(0)for i, v :=range a {
//range returns both the index and value
fmt.Printf("%d the element of a is %.2f\n", i, v)
sum += v
}
fmt.Println("\nsum of all elements of a", sum)// 0 the element of a is 13.14// 1 the element of a is 14.13// 2 the element of a is 15.20// 3 the element of a is 21.00// 4 the element of a is 52.00// sum of all elements of a 115.47
三. Slices切片
1. Creating a slice
c :=[]int{
555,666,777}
fmt.Println(c)// [555 666 777]
a :=[5]int{
76,77,78,79,80}var b []int= a[1:4]// creates a slice from a[1] to a[3]
fmt.Println(b)// [77 78 79]
2. Modifying a slice
darr :=[...]int{
57,89,90,82,100,78,67,69,59}
dslice := darr[2:5]// 90 82 100
fmt.Println("array before", darr)// array before [57 89 90 82 100 78 67 69 59]for i :=range dslice {
dslice[i]++// 每一位数字+1}
fmt.Println("array after", darr)// array after [57 89 91 83 101 78 67 69 59]// 实例2
numa :=[3]int{
78,79,80}
nums1 := numa[:]//creates a slice which contains all elements of the array
nums2 := numa[:]
fmt.Println("array before change 1", numa)// [78 79 80]
nums1[0]=100
fmt.Println("array after modification to slice nums1", numa)// [100 79 80]
nums2[1]=101
fmt.Println("array after modification to slice nums2", numa)// [100 101 80]
3. Length and capacity of a slice
fruitarray :=[...]string{
"apple","orange","grape","mango","water melon","pine apple","chikoo"}
fruitslice := fruitarray[1:3]
fmt.Printf("length of slice %d capacity %d",len(fruitslice),cap(fruitslice))//length of fruitslice is 2 and capacity is 6
fruitslice = fruitslice[:cap(fruitslice)]
fmt.Println(fruitslice)// [orange grape mango water melon pine apple chikoo]
fmt.Println("After re-slicing length is",len(fruitslice),"and capacity is ",cap(fruitslice))// After re-slicing length is 6 and capacity is 6
4. Creating a slice using make
package main
import("fmt")funcmain(){
i :=make([]int,5,5)
fmt.Println(i)}
5. Appending to a slice
cars :=[]string{
"Ferrari","Honda","Ford"}
fmt.Println("cars:", cars,"has old length",len(cars),"and capacity",cap(cars))//capacity of cars is 3
cars =append(cars,"Toyota")
fmt.Println("cars:", cars,"has new length",len(cars),"and capacity",cap(cars))//capacity of cars is doubled to 6 容量自动变大// 实例2var names []string//zero value of a slice is nilif names ==nil{
// nil == None
fmt.Println("Slice is nil going to append")
names =append(names,"John","Like","Lisa")
fmt.Println("names contents:", names)// names contents: [John Like Lisa]}
6. Passing a slice to a function
funcSubtactOne(numbers []int){
for i :=range numbers {
// i = index numbers = values
fmt.Println(i, numbers)
numbers[i]-=2// 每次循环-2}}funcmain(){
nos :=[]int{
4,5,6}
fmt.Println("slice before function call", nos)// [4 5 6]SubtactOne(nos)//function modifies the slice
fmt.Println("slice after function call", nos)// [2 3 4]}