swift3-常量与变量,int、float、double,类型推导
发布时间:2020-12-14 06:27:31 所属栏目:百科 来源:网络整理
导读:1.变量 //变量 var str = "Hello,playground" var dd = 23 var PI = 3.14 var uu = true var me = ( "me" , 11 , "33" )me .0 me .1 me .2 PI = 3.12 2.常量 //常量 let m = 89 let u = false var a:Int var b: String print(a) //a 还没有初始化,不能使用
1.变量//变量
var str = "Hello,playground"
var dd = 23
var PI = 3.14
var uu = true
var me = ("me",11,"33")
me.0
me.1
me.2
PI = 3.12
2.常量//常量
let m = 89
let u = false
var a:Int
var b:String
print(a) //a 还没有初始化,不能使用
3.int、float、doubleInt.min //-9223372036854775808
Int.max //9223372036854775807
Int64.min //-9223372036854775808
Int64.max //9223372036854775807
let f = 15 //15
let fa = 0xF //15
let fb = 0o17 //15
let fc = 0b1111 //15
let fd = 1_000_000 //1000000
var oneThirdint = 1/3 //默认类型int,0
var oneThirdFloat:Float = 1/3 //小数点后有7位,0.3333333
var oneThirdDouble:Double = 1/3 //小数点后有16位,0.3333333333333333
print(oneThirdint) //0n
print(oneThirdFloat) //由打印可知,精确度为小数点后6位,0.333333n
print(oneThirdDouble) //精确度为小数点后15位,0.333333333333333n
4.查看推导类型type(of:XXX)var three = 3
type(of:three) //查看推导结果,Int.Type
var z = 0.14
type(of:z) //Double.Type
var PI = 314e-2 //3.14
PI = 3 + 0.14159 //3.14159
PI = Double(three) + z // 不同类型变量不能直接加减,要先类型转换,3.14
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