integers提供了三种（8， 16， 32） signed unsigned Int
Integer Bounds
let minValue = UInt8.min //0
let maxValue = UInt8.max //255
Int
let intValue = 42
Double
let pi = 3.14159
let anotherPi = 3 + 0.14159
进制
let decimalInteger = 17 //十进制
let binaryInteger = 0b1001 //二进制
let octalInteger = 0o21 //八进制
let hexadecimalInteger = 0x11 //十六进制
科学表示法
let decimalDouble = 12.1875
let exponentDouble = 1.21875e1 //e--10^
let hexadecimalDouble = 0xC.3p0 //p--2^
数字分割帮助阅读
let paddedDouble = 000123.456
let oneMillion = 1_000_000
let justOverOneMillion = 1_000_000.000_000_1
类型转换
let twoThousand: UInt16 = 2_000
let one: UInt8 = 1
let twoThousandAndOne = twoThousand + UInt16(one)
Float都转成Double
let three = 3
let pointOneFourOneFiveNine = 0.14159
let pi = Double(three) + pointOneFourOneFiveNine
let intergerPi = Int(pi) // 3