package main
import "fmt"
import "os"
var (
a int
b int
)
func testArrayParmter(arr [2]int) {
//arr传进来是个副本，所以函数内改变arr，对外部不影响
println("")
for i := range arr {
arr[i] += 1
print(arr[i])
if !(i+1 == len(arr)) {
print(",")
}
}
println("")
}
func testSliceParmter(arr []int) {
println("")
for i := range arr {
arr[i] += 1
print(arr[i])
if !(i+1 == len(arr)) {
print("^,")
}
}
println("")
}
func main() {
for i := 0; i < 5; i++ {
for j := 0; j <= i; j++ {
print("A")
}
println("")
}
a = 0x77
b = 077
const c = "i am const var"
const (
d = iota
e
f = iota
)
s := "hello" + " world"
ch := []byte(s) //将s转成字节数组
ch[0] = 'c'
s2 := string(`
ssfswerq
`)
if 1 < 2 {
if 1 > 0 && !false {
fmt.Printf("0<1<2\n")
} else {
fmt.Printf("not 0<1<2\n")
}
}
var cc complex128 = 5 + 5i
fmt.Printf("d=%d e=%d f=%d s2=%s cc=%v\n", d, e, f, s2, cc)
fmt.Printf("s=%s a=%d b=%d c=%s\n", s, a, b, c)
file, err := os.OpenFile("c:\\2.py", os.O_RDONLY, 0)
if err != nil {
fmt.Println(err)
return
}
by := []byte(s)
file.Read(by)
fmt.Println(string(by)) //读取一行
dd, err := file.Stat()
if err != nil {
fmt.Println(err)
return
}
fmt.Println(dd)
file.Close()
//3种for的使用
for i := 1; i < 2; i += 1 {
fmt.Println(i)
}
i := 2
flag := true
Here: //goto的使用
for i >= 0 {
fmt.Println(i)
i -= 1
}
for {
println("while True{}")
break
}
if flag {
flag = false
goto Here
}
j := 0
J:
for i = 0; i < 100; i++ {
for j = 0; j < 100; j++ {
if i > 5 {
break J //跳出J标签所在的循环层
}
}
}
println(i, j)
println("====range的使用====")
list := []string{"a", "b", "c"}
for k, v := range list {
println(k, v)
}
for pos, cha := range "abc" {
fmt.Printf("#pos=%d cha='%c'\n", pos, cha) //为何这个会跑到while True{}前面输出
}
println("switch的使用")
ccc := 'A'
switch { //如果switch没有表达式，它会匹配true
//转化为一个个匹配，知道为true
case '0' <= ccc && ccc <= '9':
println('0')
case 'a'-32 <= ccc && ccc <= 'f'-32:
println('a')
case 'A' <= ccc && ccc <= 'F': //不会执行
println('A')
}
switch j {
case 1:
println("case 1")
case 2:
println("case 2")
default:
println("case default")
}
ch = []byte("hhhhhh")
ch2 := []byte("hhhhhhh")
println(len(ch), len(ch2))
for pos := range ch { //比较字符串大小
switch {
case ch[pos] > ch2[pos]:
println("big")
case ch[pos] < ch2[pos]:
println("small")
}
}
println("数组的使用")
arr := [2]int{1, 2} //这两个数组都初始化为1,2
var arr2 [2]int
arr2 = arr //数组同样是值类型的：将一个数组赋值给另一个数组，会复制所有的元素
for i := range arr2 {
print(arr2[i])
}
testArrayParmter(arr)
for i := range arr2 {
print(arr[i])
}
println("")
arr3 := [...]int{1, 2, 3, 4, 5, 6, 7, 8}
println(len(arr3))
println("数组的创建")
a3 := [3][2]int{[2]int{1, 2}, [...]int{1, 2}, {3, 4}}
println(len(a3))
println("slice的使用---slice是指向数组头部的指针，且是引用类型，要用make创建")
sl := make([]int, 10) //创建了一个保存有10个元素的slice
sl[1] = 2
println(sl[1])
sl2 := arr3[2:4]
println(sl2[0], sl2[1], len(sl2), arr3[:len(arr3)])
println("使用内置函数append和copy")
sa := []int{0, 0}
sb := append(sa, 2, 2)
sc := append(sb, sa...) //{0,0,2,2,0,0}
for i := 0; i < len(sc); i++ { //会跑到goto那去
fmt.Printf("=%d=", sc[i])
}
println("")
var a4 = [8]int{0, 1, 2, 3, 4, 5, 6, 7}
var ss = make([]int, 6)
//copy最多复制的元素是两个参数数组的最小长度
n1 := copy(ss, a4[0:]) //因为s的长度为6，故此时s=={0,1,2,3,4,5}
n2 := copy(ss, ss[2:]) //由于复制重叠了，故此时s=={2,3,4,5,4,5}
println(n1, n2)
testSliceParmter(ss) //返回后ss=={3,4,5,6,5,6}
println("map的使用")
monthdays := map[string]int{
"Jan": 31, "Feb": 28, "Mar": 31,
"Apr": 30, "May": 31, "Jun": 30,
"Jul": 31, "Aug": 31, "Sep": 30,
"Oct": 31, "Nov": 30, "Dec": 31, //注意最后一个逗号不能少
}
println(monthdays["Nov"])
year := 0
for _, days := range monthdays {
year += days
}
monthdays["ckl_day"] = 31 //向map添加新项
val, ok := monthdays["ckl_day"] //判断monthdays["ckl_day"]是否存在,保存在ok中
//删除monthdays["ckl_day"]项
delete(monthdays, "ckl_day")
year2 := 0
for _, days := range monthdays {
year2 += days
}
val1, ok1 := monthdays["ckl_day"]
println(year, monthdays["ckl_day"], val, ok, year2, val1, ok1)
}