//: Playground - noun: a place where people can play

import UIKit

//var name: String = "hwl"

//var age:Int = 29

//var isman:Bool = true

var name = "hwl"//类型推导为String

var age = 29//类型推导为Int

var isman = true//类型推导为Bool

var π = 3.14159226//可以直接用π作为变量名更形象

var