Swift语言基础笔记（四）

通过前面几篇的学习，Swift的基础类型学习的差不多了，接下来就学习流程控制与条件语句和运算符

一、运算符

//: Playground - noun: a place where people can playimport UIKit//运算符Swift学习，+ - * / % > < += -= || && | & 注意不同类型需要显示强制转换var x = 10;var y = 3;var z = 0;x/yDouble(x)/Double(y);var xx = +x;var yy = -y;x += 9;if x > y{    print("10 > 3");}var capacity = 30;var volume = 50;if x > y && capacity < volume{    print("Buy it");}if x < y || capacity > volume{    print("Buy it");}else{    print("not buy it");}

二、循环语句
循环语句有for、while、do-while

//: Playground - noun: a place where people can playimport UIKit//循环语句有for、while、do-whilefor index in -99...99{    index;    index*index;}var i = -99;for ; i <= 99 ; {    i*i;    i++;}for var a = -6.28; a <= 6.28; a += 0.1 {    sin(a);}var ii = -99;var step = 1;for ; ii <= 99; ii += step{    ii * ii;    step *= 2;}var a = 10;while a > 0{    a--;}var aWin = 0;var bWin = 0;var game = 0;while aWin < 3 && bWin < 3{    game++;    let a = arc4random_uniform(6) + 1;    let b = arc4random_uniform(6) + 1;    print("a is \(a), b is \(b).", terminator:" ");    if a > b{        print("A win");        bWin = 0;        aWin++;    }else if a < b{        print("B win");        aWin = 0;        bWin++;    }else{        print("a == b");        aWin = 0;        bWin = 0;    }}let winner = aWin == 3 ? "A" : "B";print("After \(game) games \(winner) Win")print("");var aaWin = false;var bbWin = false;var agame = 0;repeat{    game++;    let a = arc4random_uniform(6) + 1;    let b = arc4random_uniform(6) + 1;    print("a is \(a), b is \(b).", terminator:" ");    if a > b{        aaWin = true;    }else if a < b{        bbWin = true;    }else{        print("a == b");    }    print("");}while !aaWin && !bbWin;let awinner = aaWin ? "A" : "B";print("After \(awinner) Win")print("");while true{    let a = arc4random_uniform(6) + 1;    let b = arc4random_uniform(6) + 1;    print("a is \(a), b is \(b).");    if a == b{        print("a == b");        continue;    }        let winner = a > b ? "A" : "B";    print("\(winner) win!");    break;}

三、条件语句

switch if-else

//: Playground - noun: a place where people can playimport UIKit//条件语句var count = 15if a > 20{print(\(a) > 20)}else{print(\(a) <= 20)}let rating = "A";switch rating{case "a", "A":    print("Great");case "b", "B":    print("Just so-so");case "c", "C":    print("It's Bad");default:    print("Error")}let score = 100;switch score{case 0:    print("You got a egg")case 1..<60:    print("You faild")case 60:    print("Just passed")case 61..<80:    print("Just so-so")case 80..<90:    print("Good")case 90..<100:    print("Great")case 100:    print("Perfect!")default:    print("Error score")}print("")//x^4 - y^2 = 15* x * y;findAnswer:for m in 1...300{    for n in i...300{        if m*m*m*m - n*n == 15*m*n{            print("m = \(m), n = \(n), left = \(m*m*m*m - n*n), right = \(15*m*n)");            break findAnswer;        }    }}//where语句的使用let point = (3, 5);switch point{case let(x, y) where x == y:    print("It's on the line x == y!");case let(x, y) where x == -y:    print("It's on the line x == -y!");case let(x, y):    print("It's just an ordinary point.");    print("The point is \(x), \(y)");}let age = 19;switch age{case 10...19:    print("You're a teenager.");default:    print("You're not a teenager.");}if case 10...19 = age{    print("You're a teenager.");}if case 10...19 = age where age >= 18{    print("You're a teenager and in a college.");}let vector = (4, 0);if case (let x, 0) = vector where x > 2 && x < 5{    print("It's the vector");}