這一節涉及的東西比較雜，各種函式和表示式，零零散散

package net.edaibu.kotlintest.FunctionAndLambda

/**
 * @author geqipeng
 *
 * @date 2017/6/1
 *
 * @time 16:39
 */

//字面函式和函式表示式

//字面函式
fun findBigOne(a: Int, b: Int): Boolean {
    return a > b
}

//函式文字語法
val sum1 = { x: Int, y: Int -> x + y }
//寫法二
val sum2: (Int, Int) -> Int =
        { x, y -> x + y }

//函式表示式
fun getSum(x: Int, y: Int): Int = x + y

//函式表示式2
fun getSum2(x: Int, y: Int): Int {
    return x + y
}

//函式表示式擴充套件
var sum = fun Int.(other: Int): Int = this + other

//資料型別智慧轉換
fun transfer(x: Any) {
    if (x is String) {
        println(x.length)
    }
}

//函式引用
fun testQuote(num: Int) = num % 2 != 0

//屬性引用
var xx = 1

//擴充套件屬性
val String.lastChar:Char
get() = 'k'


fun main(args: Array<String>) {
    println(getSum(10, 20))      //30
    println(getSum2(10, 20))     //30
    println("range_________________________")
//range
    for (i in 1..5) {
        println(i)   //12345
    }
    println("if判斷____________________________")
    var i = 5
    if (i in 1..5) {
        println(i)  //5
    }

    println("downto______________________________")
    //逆序輸出  downto
    for (i in 4 downTo 2) {
        println(i)             //432
    }
    println("reverse————————————————————————————————————————")
    for (i in (1..5).reversed())
        println(i)        //54321

    println("is 表示式————————————————————————————————————————————")
    //is表示式
    if ("哈哈" is String) {
        println("is string")   //is string
    }

    println("智慧轉換——————————————————————————————————————")
    println(transfer("hello kotlin"))   //12


    println("when表示式——————————————————————————————————")
    var x: Any = 100
    when (x) {
        is Int -> print(x)    //100
        is String -> print(x.length)
    }
    println("運算子過載————————————————————————————————————————————————")

    //運算子過載
    var a = 10
    var b = 20
    //加
    val c = a.plus(b)
    //減
    val d = a.minus(b)
    //乘
    val e = a.times(b)
    //除
    val f = a.div(b)
    //取餘
    val g = a.mod(b)
    print("__c=" + c + "_d=" + d + "_e=" + e + "_f=" + f + "_g=" + g)    //__c=30_d=-10_e=200_f=0_g=10

    //空安全
    var n: String? = "hahaha"
    n = null
    //採用？符號進行為空判斷即 n不為空才將n的長度賦值給m
    val m = n?.length
    println(m)

    //函式引用  使用符號：：來引用方法
    println("函式引用——————————————————————————————————")
    var list1 = listOf(1, 2, 3, 4)
    println(list1.filter(::testQuote))  // [1, 3]

    println("屬性引用______________________________")
    println(::xx.get())   //1
    ::xx.set(2)           //通過set方法來進行賦值
    println(::xx.get())   //2

    println("擴充套件屬性_______________________________")
    println(String::lastChar.get("kotlin"))    // k


}