go语言中的选择与循环

package main

import (
    "fmt"
    "strings"
    "time"
)

func main(){
    // 布尔类型
        // true和false是go语言中两个已经声明好的常量
        // go语言只有true是真的，只有false是假的。和其他语言如js不同，js会将""这种字符串当作false，其他的字符串当作true
    
    // strings.Contains
        // 来自strings包的Contains()函数可以判断某个字符串是否包含另外一个字符串
    fmt.Println("You find yourself in a dimly lit cavern.")

    var command = "walk outside"
    var exit = strings.Contains(command, "outside")
    fmt.Println("You leave the cave:", exit)

    // 比较运算符
        // 如果我们比较两个值，得到的结果也是true或false
    fmt.Println("There is a sign near the entrance that reads 'No Minors'.")

    var age = 41
    var minor = age < 18
    fmt.Printf("At age %v, am I a minor? %v\n", age, minor) 

    // 使用if来做分支
    var commands = "go east"

    if commands == "go east"{
        fmt.Println("You head further up the mountain.")
    } else if commands == "go inside" {
        fmt.Println("You enter the cave where you live out the rest of your life.")
    } else {
        fmt.Println("Didn't quite get that.")
    }

    // 逻辑运算符
        // ||表示或、&&表示与，它们通常用来检测多个条件
    fmt.Println("The year is 2020, should you leap?")

    var year = 2020
    var leap = year % 400 == 0 || (year % 4 == 0 && year % 100 != 0)

    if leap {
        fmt.Println("Look before you leap!")
    } else {
        fmt.Println("Keep your feet on the ground.")
    }

    // 取反逻辑运算符!
    var haveTorch = true
    var litTorch = false
    
    if !haveTorch || !litTorch {
        fmt.Println("Nothing to see here.")
    }

    // 使用switch做分支
        // switch语句也可以对数字进行匹配
        // 还有一个fallthrough关键字，它用来执行下一个case的body部分，这一点与C++等语言不同！
    fmt.Println("There is a cavern entrance here and a path to the east.")
    var commandss = "go inside"

    switch commandss {
    case "go east":
        fmt.Println("You head further up the moutain.")
    case "enter cave", "go inside":
        fmt.Println("You find yourself in a dimly lit cavern.")
    case "read sign":
        fmt.Println("The sign reads 'No Minors'.")
    default:
        fmt.Println("Didn't quite get that.")
    }

    // fallthrough关键字
    var room = "lake"
    switch {
    case room == "cave":
        fmt.Println("You find yourself in a dimly lit cavern.")
    case room == "lake":
        fmt.Println("The ice seems solid enough.")
        fallthrough
    case room == "underwater":
        fmt.Println("The water is freezing cold.")
    }

    // 使用循环做重复
        // for关键字可以让你的代码重复执行
        // for后面没有跟条件，就是无限循环
        // 可以使用break来跳出循环
    var count = 10
    for count > 0 {
        fmt.Println(count)
        time.Sleep(time.Second * 2)
        count--
    }
    fmt.Println("Liftoff!")
}