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!") }