一.demo
1 单包程序运行
package main //注意要有src目录?
//F:\Program Files\go\goprojects\src\project1\main包\main.go
import "fmt"
func main() {
s1 := "[1]建议换行符号'\\r\\n' windows='\\n' linux='\\r\\n'\n\r"
s2 := "go run main.go\t\tgo build main.go\tmain.exe\r\n"
s3 := "gofmt main.go\t\tgofmt -w main.go"
fmt.Println(s1, s2, s3)
var str1 string = "\r\n[vscode]\r\nshiftAlt上下箭头=复制当前行\r\n"
var str2 = "CtrlShiftK=删除当前行+下一行变成当前行\r\n"
str3 := "CtrlShiftEnter=上面新增1行\r\n"
str4 := "某行首字符前面 点击键盘Tab shiftTab=缩进代码\n"
fmt.Printf("%s%s%s%v", str1, str2, str3, str4)
fmt.Print("vscode_File(Edit)有快捷键提示\n\r")
}
/*shiftAltA=选中需要添加或者取消多行注释 ctrl/=该行 添加或取消单行注释
Vscode_File_prefence_setting 搜索框
1 Files: Auto Save =onFocusChange 自动保存
2 editor.fontSize =19 editor.fontWeight 默认"normal"
3 extension.autoUpdate =false(None) //取消扩展自动更新 以后无通知
4 Update: Enable Windows Background Updates //启用后台更新可以取消
5 editor.quickSuggestions //建议提示 需要配套扩展插件使用
*/2 多包的主程序运行
package utils //推荐习惯(包名=当前目录名一致）不一致也可以但不推荐
//F:\Program Files\go\goprojects\src\project1\utils包\utils.go
//注意需要src目录
import (
"fmt"
)
func Cal(n1 float64, n2 float64, operator byte) float64 {
//注意 函数名称首字母大写=public 小写=private
var res float64
switch operator {
case '+':
res = n1 + n2
case '-':
res = n1 - n2
case '*':
res = n1 * n2
case '/':
res = n1 / n2
default:
fmt.Println("操作符号错误...")
}
return res
}package main
//F:\Program Files\go\goprojects\src\project1\main包目录\main.go
//注意有src目录?
import (
"fmt"
"project1/utils" //出现错误?
)
func main() {
fmt.Printf("【1】%v\t【2】%v\n", cal(3, 4, '+'), cal(2.2, 1.1, '-'))
fmt.Printf("【3】%v %v\n", utils.Cal(3, 4, '/'), utils.Cal(3, 4, '*'))
}
func cal(n1 float64, n2 float64, operator byte) float64 {
var res float64
switch operator {
case '+':
res = n1 + n2
case '-':
res = n1 - n2
case '*':
res = n1 * n2
case '/':
res = n1 / n2
default:
fmt.Println("操作符号错误...")
}
return res
}
/*
【多个包的程序运行】
1.配置环境变量 GOPATH=F:\Program Files\go\goprojects
2.vscode配置GOPATH File_preference_setting输入go.gopath修改后重启vscode
3.Gopath路径下cmd
go env -w GO111MODULE=off
go build -o bin/my.exe project1/main （进入bin目录运行 my.exet程序）
4.也可以直接运行vscode的main.go代码
*/3 数据类型1
package main
import (
"fmt"
"math"
"unsafe" //unsafe.Sizeof该方法可以求出对象的字节长度
)
var (
pl, pf = fmt.Println, fmt.Printf
)
func main() { f8() }
func f1() {
var j0 int8 //有符号int8 1字节范围=-128~127 声明未赋值=0
var j1, j2 int8 = -128, 127
pl("【1】", j0, j1, j2) //右边int字面类型根据左边调整为int8
var i0, i1, i2, i3, i4 uint8 = byte(0), 255, 'a', 'A', '0'
pl("【2】", i0, i1, i2, i3, i4, "\t无符号int8=0~256")
var b0, b1, b2, b3 byte = 0, byte(255), 'a', 'z'
b4, b5, b6, b7 := 'A', 'Z', '0', '9'
pl("【3】", b0, b1, b2, b3, b4, b5, b6, b7, "byte=uint8")
pf("【4】(%T %T %T) (%p %p %p)\n", j0, i0, b0, &b0, &b1, &b2)
pl(unsafe.Sizeof(j0), unsafe.Sizeof(i0), unsafe.Sizeof(b0))
/* shiftAltA vscode可直接识别下面代码错误 暂未找到方法忽略错误
fmt.Println(uint8(-1), uint8(256), int8(-129), int8(128))
*/
}
func f2() { //占2个字节 vscode=CtrlS保存后运行程序
var i1, i2, i3 uint16 = 0, uint16(math.Exp2(16) - 1), 65535
fmt.Println("【1】", i1, i2, i3, "使用强制类型转换")
pf("【2】%T (%p %v %x %p)\n", i1, &i1, &i2, &i3, &i3)
var j1, j2 = int16(-math.Exp2(15)), int16(math.Exp2(15) - 1)
var j3, j4 int16 = -32768, 32767
pl("【3】")
pf("(%T %p %x %v) 强制类型转换\r\n", j1, &j1, j1, j1)
pf("(%T %p %x %v %d)\r\n", j2, &j2, j2, j2, j2)
pf("(%T %p %x %v)\r\n", j3, &j3, j3, j3)
pf("(%T %p %x %v)\r\n", j4, &j4, j4, j4)
}
func f3() { //占4个字节 rune是int32别名 byte是uint8别名
var i1, i2 uint32 = 0, uint32(math.Exp2(32) - 1)
pf("i=(%v %d %T %p) i2=(%p %v)\n", i1, i1, i1, &i1, &i2, i2)
j1, j2 := int32(-math.Exp2(31)), int32(math.Exp2(31)-1)
pl(&j1, &j2, j1, j2)
}
func f4() { //占8字节
var m64, m63, m62 float64 = math.Exp2(64), math.Exp2(63), math.Exp2(62)
fmt.Printf("%T %v %v %v\n", m64, m64, m63, m62)
pf("%v %v %v %v\n", uint64(m64), uint64(m63), uint64(m62)*2)
var arr [4]uint64 = [4]uint64{0, 2*uint64(m63) - 1}
pl(arr, &(arr[1]), &(arr[0]))
arr2 := [...]int64{int64(-m63), int64(int64(m63) - 1)}
pl(arr2, &(arr2[1]), &(arr2[0]), "相差8字节")
}
func f5() {
var i0 int
i1, i2 := 100, 200
var i3 int
i3 = 300
pl(i0, i1, i2, i3, &i0, &i1, &i2, &i3)
pf("%T %T %T %T %T\r\n", math.Exp2(2), 4, int8(4), byte(4), uint8(4))
pf("%T %T %T %T\r\n", int16(4), int32(4), rune(4), int64(4))
}
func f6() {
var v1 int
var v2 float32
var v3 float64
var v4 bool
var v5 string
var v6 byte = 'a'
pf("【1】%d %f %.2f %t %s空串 %c\n", v1, v2, v3, v4, v5, v6)
pf("【1】%v %v %v %v %v空串 %v\n", v1, v2, v3, v4, v5, v6)
pf("【1】%x %x %x %x %x空串 %x\n", v1, v2, v3, v4, v5, v6)
pf("【1】%x %x %x %x %x %x\n", &v1, &v2, &v3, &v4, &v5, &v6)
fmt.Print("【2】", unsafe.Sizeof(v1), unsafe.Sizeof(v2), unsafe.Sizeof(v3), "\t")
fmt.Println(unsafe.Sizeof(v4), unsafe.Sizeof(v5), unsafe.Sizeof(byte(200)))
var n1, price = 100, 99.99
fmt.Printf("【3】100默认%T-字节数%d 99.99默认=%T\n", n1, unsafe.Sizeof(n1), price)
f1, f2, f3, f4, f5 := 0.123, 0.01234567890123456789, 9e+5, 9e+6, 9e7
fmt.Println("【4】", f1, f2, f3, f4, f5)
}
func f7() { //1 高类型(强)转低 溢出处理不报错 右边立即数是int64类型 自动根据左边转换
var i int32 = 100
fmt.Printf("【1】(%T %v) (%T %v)\n", i, i, int8(i), int8(i))
var j = math.Exp2(15) - 1
fmt.Printf("【2】[%T %v] [%T %v]\n", j, j, int8(j), int8(j))
//2 低类型转化为高(低精度转高) 其它语言会自动转化
var f float32 = float32(i)
fmt.Printf("%T %v \n", f, f)
}
func f8() { //必须是相同类型才能相加 其它语言会自动转化高类型
var i int64 = 10
var j int32 = 20 //i+j会报错 一定声明强转 i+int64(j) 或者int32(i)+j
x := int64(i) + int64(j) //相加结果如果超出范围 按照溢出处理
y := int8(i) + 127 //如果加128 则报错? 自动转化低类型
fmt.Println(i, j, x)
fmt.Printf("%T %v", y, y)
}3 数据类型2
package main
import (
"fmt"
_ "math"
"strconv"
"unsafe"
)
func main() { g1() }
func f1() { //【字符】
var i1, i2, i3, i4 uint8 = 'a', 'z', 'A', 'Z'
i5, i6 := '0', '9'
fmt.Printf("%T %d %c\t", i1, unsafe.Sizeof(i1), 'a'+10)
fmt.Println(i1, i2, i3, i4, i5, i6, 'a'+10)
var c1, c2, c3, c4, c5, c6 byte = 'a', 'z', 'A', 'Z', '0', '9'
fmt.Printf("%T %d\t", i1, unsafe.Sizeof(c1))
fmt.Println(c1, c2, c3, c4, c5, c6)
var C1, C2 int = '中', '国'
fmt.Println(C1, C2, 'a'+10)
fmt.Printf("%c (%T %c %v)\n", C1, C2, C2, C2)
}
func f2() { //【字符串】长度为什么都是16?
var a string = "【1】统一UT8编码\n一旦赋值不可变\t" +
"address[0]=\"a\"错误\n"
fmt.Printf("%s %T %d %p %d\n", a, a, unsafe.Sizeof(a), &a, len(a))
code := `【2】
使用反引号=在Tab键上方的符号\n 批量输入多行\t字符串
`
fmt.Printf("%s\n%T\n", code, code)
fmt.Printf("%d %p %d\n", unsafe.Sizeof(code), &code, len(code))
var str = "abc"
fmt.Printf("%s %v %T\n", str, str, str)
fmt.Printf("%v %p %v\n", unsafe.Sizeof(str), &str, len(str))
arr := [...]string{"abc", "def", "ghi"}
fmt.Println(arr, &(arr[0]), &(arr[1]), &(arr[2]))
fmt.Printf("%T %p\n", &(arr[1]), &(arr[1]))
fmt.Printf("%T %p\n", &arr[1], &arr[1])
fmt.Println(fmt.Sprintf("%d", &arr[0]))
fmt.Println(fmt.Sprintf("%d", &arr[1]))
fmt.Println(fmt.Sprintf("%d", &arr[2]))
s := fmt.Sprintf("%d", &arr[2])
i1, err1 := strconv.Atoi(s)
i2, err2 := strconv.ParseInt(s, 10, 64) //0八进制 10 16
fmt.Printf("%T %T %v (%v %v)\n", s, i1, err1, i2, err2)
}
func f3() { //【fmt.Sprintf】
num1, num2 := int(99), float64(23.456)
var s1, s2 string = fmt.Sprintf("%d", num1), fmt.Sprintf("%f", num2)
fmt.Printf("【1】%T: %v %q \n", s1, s1, s1) //%q=带双引号"值"
fmt.Printf("【2】%T: %v %q \n", s2, s2, s2)
fmt.Println("【3】", fmt.Sprintf("布尔(\"%t\")", true))
fmt.Println("【4】", fmt.Sprintf("%c", 'm'))
}
func f4() { //【strconv.FormatInt FormatFloat Itoa FormatBool】
s1 := strconv.FormatInt(int64(99), 10)
s2 := strconv.FormatFloat(23.456, 'f', 10, 64)
fmt.Printf("【1】(%T %v %q) (%T %v %q)\n", s1, s1, s1, s2, s2, s2)
fmt.Printf("【2】%q %T\n", strconv.Itoa(99), strconv.Itoa(99))
s3 := strconv.FormatBool(true)
fmt.Printf("【3】%T %v", s3, s3)
}
func g1() {
var s1, s2, s3, s4 = "true", "123456", "123.456", "hello"
var b bool
var n1 int64
var n2 int
var f1 float64
var f2 float32
b, _ = strconv.ParseBool(s1)
n1, _ = strconv.ParseInt(s2, 10, 64)
n2 = int(n1)
f1, _ = strconv.ParseFloat(s3, 64)
f2 = float32(f1)
fmt.Printf("%T:%v \t %T:%v \t %T:%v\n", b, b, n1, n1, n2, n2)
fmt.Printf("%T:%v \t %T:%v\n", f1, f1, f2, f2)
E1, e := strconv.ParseInt(s4, 10, 64)
fmt.Printf("%s %T:%v [err]%v\n", s4, E1, E1, e)
bool_value, e := strconv.ParseBool(s4)
fmt.Println(bool_value, e) //异常已经写在方法本身之中
}4 运算
package main
import (
"fmt"
_ "math"
_ "strconv"
_ "unsafe"
)
func main() { z2() }
func f1() {
var v0, v1 int
v1 = 1
var v2 int = 2
var v3 = 10.11
v4 := "Tom"
fmt.Println(v0, v1, v2, v3, "\n两串相加拼接=", v4+"tom")
}
func f2() {
var n1, n2, n3 int
n1, n2, n3 = 11, 12, 13
fmt.Println("\"int n1 n2 n3=\"", n1, n2, n3)
var p1, p2, p3 = 21, "zhangsan", 10.11
s1, s2, s3 := 31, "32aa", 33.33
fmt.Println(p1, p2, p3, "\t", s1, s2, s3)
}
func f3() {
sum, sub := getVal(30, 20)
fmt.Println("sum=", sum, "sub", sub)
sum2, _ := getVal(100, 50)
fmt.Println("sum2=", sum2)
}
func getVal(num1 int, num2 int) (int, int) {
sum := num1 + num2
sub := num1 - num2
return sum, sub
}
func f4() { //值类型=常量变量直接存储值通常在内存栈中分配
var i int = 100 //引用类型=指针 slice切片 map 管道chan interface等
var ptr *int = &i //引用类型 通常在内存堆分配空间
fmt.Printf("i地址:%v i值:%d\n", &i, i)
fmt.Printf("ptr=%v ptr地址=%v ptr指向值=%v\n", ptr, &ptr, *ptr)
}
func g1() { //1.算式运算符 +-=正号负号加减/字符相加拼接 */% ++ --
fmt.Println(10/3, 10%3, -10/3, -10%3, 10.0/4, "取余公式=", 10-(10/3)*3)
var i int = 10
var j int = 10
i++ //报错 var a int = i++ 或 j--; i++ j--只能独立使用; 没有++i
j-- //报错 if i++>0 {};设计理念减少歧义; 没有--j
var a, b int = i, j
fmt.Println(i, j, a, b)
}
func g2() { //2.比较运算符/关系运算符 返回值bool类型
var n1 int = 9
var n2 int = 8
fmt.Println(n1 == n2, n1 != n2, n1 > n2, n1 >= n2, n1 < n2, n1 <= n2)
}
func g3() { //3.逻辑
var age int = 40
if age >= 30 && age <= 50 {
fmt.Println("ok1:", age >= 30 && age <= 50)
}
fmt.Println(age > 60 || age < 18, !(age > 30))
fmt.Println("[短路与false]", age > 50 && age < 60)
fmt.Println("[短路与true]", age > 30 || age < 10)
}
func z1() {
var i, j, k, l int = 5, 011, 0x11, 0x11
fmt.Println(i, j, k, l)
fmt.Printf("i=[%b,%o,%d,%x]\t", i, i, i, i) //%t=bool值
fmt.Printf("j=[%b,%o,%d,%X]\n", j, j, j, j)
var a1, a2 int = 1 >> 2, 1 << 2 //右移两位相当于整除2 左移两位乘4(除了高位溢出)
fmt.Println(a1, a2) //右移高位补符号 左移后补0
var b1 int = -1 >> 2 //正整数=原码=补码 负整数补码=正整原码取反+1
var b2 int = -1 << 2 //左移2位=1100 真值=-(取反0011+1=0100)=-4
fmt.Println(b1, b2) //-1补=1111右移不变
fmt.Println(2&3, 2|3, 2^3, "\t", 0b010&0b011, 0b010|0b011, 0b010^0b011)
}
func z2() { //6.其它 如*取(地址)指向值 &取(常量变量的)地址
var n string
var age byte
var salary float32
var isPass bool
fmt.Printf("请输入姓名: ")
fmt.Scanln(&n) //中断执行
fmt.Printf("年龄: ")
fmt.Scanln(&age)
fmt.Printf("薪水: ")
fmt.Scanln(&salary)
fmt.Printf("是否全职: ")
fmt.Scanln(&isPass)
fmt.Printf("姓名:%v 年龄:%v 薪水:%v 全职:%v\n", n, age, salary, isPass)
fmt.Printf("请输姓名,年龄,薪水,是否通过考试,以空格隔开: ")
fmt.Scanf("%s %d %f %t\n", &n, &age, &salary, &isPass)
fmt.Printf("姓名:%v 年龄:%v 薪水:%v 全职:%v\n", n, age, salary, isPass)
}
