go变量与常量

package main

import (
	"fmt"
)

var v1, v2 int

// 这种因式分解关键字的写法一般用于声明全局变量
var (
	global_ivalue int
	global_bvalue bool
)

func fun1() (int, int, string) {
	return 1, 2, "str3"
}

func main() {
	global_ivalue, global_bvalue = 3, true
	fmt.Println("global_ivalue:", global_ivalue, ",global_bvalue:", global_bvalue)
	v1, v2 := 1, 2
	fmt.Println("v1:", v1, ",v2:", v2)
	var v3, v4 = 3, "str4"
	fmt.Println("v3:", v3, ",v4:", v4)

	//必须有var才能直接用=,否则需要:=
	var _, r2, r3 = fun1()
	fmt.Println("r2:", r2, ",r3:", r3)
}

global_ivalue: 3 ,global_bvalue: true
v1: 1 ,v2: 2
v3: 3 ,v4: str4
r2: 2 ,r3: str3

package main

import (
	"fmt"
	"unsafe"
)

var v1, v2 int

// 这种因式分解关键字的写法一般用于声明全局变量
var (
	global_ivalue int
	global_bvalue bool
)

func fun1() (int, int, string) {
	return 1, 2, "str3"
}

func main() {
	global_ivalue, global_bvalue = 3, true
	fmt.Println("global_ivalue:", global_ivalue, ",global_bvalue:", global_bvalue)
	v1, v2 := 1, 2
	fmt.Println("v1:", v1, ",v2:", v2)
	var v3, v4 = 3, "str4"
	fmt.Println("v3:", v3, ",v4:", v4)

	//必须有var才能直接用=,否则需要:=
	var _, r2, r3 = fun1()
	fmt.Println("r2:", r2, ",r3:", r3)

	const c1, c2, c3 = 1, false, "str"
	var c4 = unsafe.Sizeof(v1)
	fmt.Println("const size:", c4)

	//<<=	左移后赋值	C <<= 2 等于 C = C << 2
	var c = 3
	c <<= 2
	fmt.Println("c:", c)

	//指针类型
	var ptr *int
	ptr = &v1
	fmt.Println("point:", *ptr)
}

global_ivalue: 3 ,global_bvalue: true
v1: 1 ,v2: 2
v3: 3 ,v4: str4
r2: 2 ,r3: str3
const size: 8
c: 12
point: 1

package main

import "fmt"

//iota，第一次出现为0,接下来枚举每一行加1,相当于行索引
const (
	a = iota
	b
	c = "c"
	d = iota
)

func main() {
	fmt.Println(a, b, c, d)

}
0 1 c 3