Go语言浮点类型(小数)

浮点型表示存储的数据是实数,如 3.145。关于浮点型的说明,如下所示:

类型字节数说明
float32432 位的浮点数
float6464 位的浮点数

浮点数的声明方式如下所示:

var x float32   // 声明 32 位浮点数
var y float64   // 声明 64 位浮点数常量 math.MaxFloat32 表示 float32 能获取的最大值,大约是 3.4×1038;常量 math.SmallestNonzeroFloat32 表示 float32 能获取的最小值,大约为 1.4×10-45

常量 math.MaxFloat64 表示 float64 能获取的最大值,大约是 1.8×10308;常量 math.SmallestNonzeroFloat64 表示 float64 能获取的最小值,大约为 4.9×10-324

Go语言匿名变量

Go语言的函数可以返回多个值,而事实上并不是所有的返回值都用得上,那么就可以使用匿名变量。匿名变量的特点是一个下画线__本身就是一个特殊的标识符,被称为空白标识符。它可以像其他标识符那样用于变量的声明或赋值(任何类型都可以赋值给它),但任何赋给这个标识符的值都将被抛弃,因此这些值不能在后续的代码中使用,也不可以使用这个标识符作为变量对其它变量进行赋值或运算。

使用匿名变量时,只需要在变量声明的地方使用下画线替换即可,下面通过一个简单的示例来演示一下。

【示例】定义一个函数,功能为返回两个 int 类型变量,第一个返回 10,第二个返回 20,第一次调用舍弃第二个返回值,第二次调用舍弃第一个返回值,具体语法格式如下所示。

package main
import (
    "fmt"
)
func GetData() (int, int) {
    return 100, 200
}
func main() {
    a, _ := GetData() // 舍弃第二个返回值
    _, b := GetData() // 舍弃第一个返回值
    fmt.Println(a, b)
}

运行结果如下:

100 200匿名变量不占用内存空间,不会分配内存,而且匿名变量与匿名变量之间也不会因为多次声明而无法使用。

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Go语言变量多重赋值

变量多重赋值是指多个变量同时赋值。在Go语言语法中,变量初始化和变量赋值是两个不同的概念,Go语言的变量赋值与其他语言一样,但是Go语言提供了其他程序员期待已久的多重赋值功能,可以实现变量交换。多重赋值让Go语言比其他语言减少了代码量。

以简单的算法交换变量为例,传统写法如下所示。

var a int = 10
var b int = 20
var tmp int
tmp = a
a = b
b = t新定义的变量是需要内存的,于是有人设计了新的算法来取代中间变量,其中一种写法如下所示。

var a int = 10
var b int = 20
a = a ^ b
b = b ^ a
a = a ^ b以Go语言的多重赋值功能为例,写法如下所示。

var a int = 10
var b int = 20
b, a = a, b从以上例子来看,Go语言的写法明显简洁了许多,需要注意的是,多重赋值时,左值和右值按照从左到右的顺序赋值。这种方法在错误处理和函数当中会大量使用。

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Go语言编码规范

1、注释

注释就是对代码功能进行的解释,方便开发人员理解被注释的代码,Go语言中有以下两种形式。

  • 单行注释:是最常见的注释形式,可以在任何位置使用以//开头的单行注释;
  • 多行注释:也叫块注释,均以/*开头,并以*/结尾,且不可以嵌套使用。多行注释一般用于文档描述或注释成块的代码片段。

2、分隔符

程序中可能会使用到的分隔符包括括号( )、中括号[ ]和大括号{ };程序中可能会使用到的标点符号,如下表所示。

   符号名称      符号   
 .
逗号 ,
分号 ;
冒号 :
省略号 …

3、Go语言的空格

Go语言中变量的声明必须使用空格隔开,例如var age int

在Go语言代码中适当使用空格能够让程序更容易阅读,在变量与运算符之间加入空格,可以使程序看起来更加美观,例如:

a = x + y

4、语句的结尾

在Go语言程序中,换行代表着一个语句结束,并不需要像 Java 那样以分号结尾,因为这些工作都将由Go编译器自动完成。

如果打算将多个语句写在同一行,那么则必须使用分号;将它们人为区分,但在实际开发中并不建议将多行代码写在同一行。

5、可见性规则

Go语言中,通常使用大小写来决定标识符(常量、变量、类型、接口、结构或函数)是否可以被外部包所调用。

如果标识符以一个大写字母开头,那么其对象就可以被外部包的代码所使用(使用时程序需要先导入这个包),类似面向对象语言中的 public;如果标识符以小写字母开头,那么它对于外部包则是不可见的,但是它们在整个包的内部是可见并且可用的,类似面向对象语言中的 private。

本文章引用自 http://www.weixueyuan.net/(因感觉收获甚多,特地收藏,如有侵权,联系作者,必删)

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