声明变量和nil【go语言】

1 基本数据类型和struct声明时都有初始值，不能和nil进行比较

	var a int
	fmt.Printf("-------&q=%p  type:%T   v:%v\n", &a, a, a)
	var float1 float32
	fmt.Printf("-------&q=%p  type:%T   v:%v\n", &float1, float1, float1)
	var complex1 complex128
	fmt.Printf("-------&q=%p  type:%T   v:%v\n", &complex1, complex1, complex1)
	var b bool
	fmt.Printf("-------&q=%p  type:%T   v:%v\n", &b, b, b)
	var str string
	fmt.Printf("-------&q=%p  type:%T   v:%v\n", &str, str, str)
	type struct1 struct {
		iii   int
		bbb   int
		inter interface{}
	}
	var struc struct1
	fmt.Printf("-------&q=%p  type:%T   v:%v\n", &struc, struc, struc)

输出：
-------&q=0xc000060058  type:int   v:0
-------&q=0xc000060090  type:float32   v:0
-------&q=0xc0000600a0  type:complex128   v:(0+0i)
-------&q=0xc000060094  type:bool   v:false
-------&q=0xc00004c1f0  type:string   v:
-------&q=0xc000058440  type:main.struct1   v:{0 0 <nil>}

2 常量值是没有地址的

	const const1 = "hello"
	fmt.Printf("-------&q=%p  type:%T   v:%v\n", const1, const1, const1)
	输出：
	&q=%!p(string=hello)  type:string   v:hello

3 指针，函数值，slice，map，chan，interface声明时都是默认为nil

	var strPointer *string
	fmt.Printf("-------&q=%p  type:%T   v:%v  is nil:%v\n", &strPointer, strPointer, strPointer, strPointer == nil)
	var f func(int) int
	fmt.Printf("-------&q=%p  type:%T   v:%v  is nil:%v\n", &f, f, f, f == nil)
	var s []int
	fmt.Printf("-------&q=%p  type:%T   v:%v  is nil:%v\n", &s, s, s, s == nil)
	var m map[string]string
	fmt.Printf("-------&q=%p  type:%T   v:%v  is nil:%v\n", &m, m, m, m == nil)
	var c chan int
	fmt.Printf("-------&q=%p  type:%T   v:%v  is nil:%v\n", &c, c, c, c == nil)
	var i interface{}
	fmt.Printf("-------&q=%p  type:%T   v:%v  is nil:%v\n", &i, i, i, i == nil)
	
输出：
-------&q=0xc00008c020  type:*string   v:<nil>  is nil:true
-------&q=0xc00008c020  type:func(int) int   v:<nil>  is nil:true
-------&q=0xc0000564a0  type:[]int   v:[]  is nil:true
-------&q=0xc00008c028  type:map[string]string   v:map[]  is nil:true
-------&q=0xc00008c030  type:chan int   v:<nil>  is nil:true
-------&q=0xc00004c200  type:<nil>   v:<nil>  is nil:true