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fun add(a:Int,b:Int):Int= a+b

fun hof(a:Int,b:Int,func:(Int,Int)->Int)=func(a,b)

fun main() {
    val result1:Int=hof(3,4,::add)
    println("result1=$result1")
    val result:Int=hof(1,2,func={a:Int,b:Int->a+b})
    //val result:Int=hof(1,2){a:Int,b:Int->a+b}
    println("result=$result")

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package localfunctions

fun first(): (Int) -> Int {
	val func = fun(i: Int) = i + 1
	return func
}

fun second(): (String) -> String {
	val func2 = { s: String -> "$s!" }
	return func2

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package main

class Constructors(val color:String){
    init {
        println("Init Color=$color")
    }
    //val or var is not allowed on secondary constructors
    //You cannot declare a return type for a secondary constructor
    constructor(color:String,value:Int):this(color){
        println("Color=$color,Value=$value")

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#Scope Functions in Kotlin

	this Context	it Context
Produces last expression	with,run	let
Produces receiver	apply	also

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package main

open class Pet
class Dog:Pet()

inline fun <reified T>check(t:Any)=t is T

fun main(){
    var isValid:Boolean=check<Pet>(Dog())
    println(isValid)

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package main

data class Num(var value:Int)

infix fun Num.plus(num:Int)=value + num

operator fun Num.plus(num:Num)=value+num.value

fun main(){
    var result=Num(4) plus 3

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package main
//Covarient example start
interface Source<out T> {
    fun nextT(): T
}

class Complement<Int>(var num:Int):Source<Int>{
    override fun nextT()=num
    override fun toString()="${this::class.simpleName}"
}

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package main
abstract class AB
interface INTF
open class X
data class Y:X()
sealed class Z
class A{
    class B
    inner class C
    object D{//can implement interfaces

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// PropertyDelegation/FileDelegate.kt
package propertydelegation

import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty
import checkinstructions.DataFile

class FileDelegate :
        ReadWriteProperty<Any?, String> {
    override fun getValue(

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//Zipping

//Flattening

//Sequences (Lazy mapping)