这里省略了关键字var，我很喜欢这种方式（可以少写代码，而没有任何坏处）。但这有需要注意的是“ :=” 是在声明和初始化变量，因此该变量必须是第一次出现，如下初始化是错误的。但是要注意赋值时要确定你想要的类型，在Go中不支持隐式转换的。如果是定义个float64类型的变量，请写为 v1 :=8.0而不是v1 :=8 。

var a int

a := 8

//我刚开始时老出现这种错误，一直将 “:= ” 当作一般赋值语句处理

思考问题

初始化语句，在编译器上是如何进行自动类型推导的。一些字面常量是如何归类的？

如 8 → int , 8.0 → float64

package main

import (

"fmt"

"reflect"

)

func main(){

var v1 int = 8

var v2 byte = 8

v3 := 8

v4 := 8.0

fmt.Printf("v1 type :%s\n",reflect.TypeOf(v1)) //int

fmt.Printf("v2 type :%s\n",reflect.TypeOf(v2)) //uint8

fmt.Printf("v3 type :%s\n",reflect.TypeOf(v3)) //int

fmt.Printf("v4 type :%s\n",reflect.TypeOf(v4)) //float64

}

官方文档： http://golang.org/ref/spec#Constant_expressions

const a = 2 + 3.0          // a == 5.0   (untyped floating-point constant)
const b = 15 / 4           // b == 3     (untyped integer constant)
const c = 15 / 4.0         // c == 3.75  (untyped floating-point constant)
const Θ float64 = 3/2      // Θ == 1.0   (type float64, 3/2 is integer division)
const Π float64 = 3/2.     // Π == 1.5   (type float64, 3/2. is float division)
const d = 1 << 3.0         // d == 8     (untyped integer constant)
const e = 1.0 << 3         // e == 8     (untyped integer constant)
const f = int32(1) << 33   // f == 0     (type int32)
const g = float64(2) >> 1  // illegal    (float64(2) is a typed floating-point constant)
const h = "foo" > "bar"    // h == true  (untyped boolean constant)
const j = true             // j == true  (untyped boolean constant)
const k = 'w' + 1          // k == 'x'   (untyped rune constant)
const l = "hi"             // l == "hi"  (untyped string constant)
const m = string(k)        // m == "x"   (type string)
const Σ = 1 - 0.707i       //            (untyped complex constant)
const Δ = Σ + 2.0e-4       //            (untyped complex constant)
const Φ = iota*1i - 1/1i   //            (untyped complex constant)

const ic = complex(0, c) // ic == 3.75i (untyped complex constant)

const iΘ = complex(0, Θ)   // iΘ == 1.5i   (type complex128)

const Huge = 1 << 100

// Huge == 1267650600228229401496703205376 (untyped integer constant)

const Four int8 = Huge >> 98  // Four == 4      (type int8)

^1 // untyped integer constant, equal to -2

uint8(^1)  // illegal: same as uint8(-2), -2 cannot be represented as a uint8
^uint8(1)  // typed uint8 constant, same as 0xFF ^ uint8(1) = uint8(0xFE)
int8(^1)   // same as int8(-2)
^int8(1)   // same as -1 ^ int8(1) = -2

转载时请注明出处！老虞http://www.cnblogs.com/howDo/

分类: GoLang

标签: GoLang

分类: go语言

posted on 2013-04-13 12:16 HackerVirus 阅读(226) 评论(0) 编辑收藏举报

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