lesson4
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@ -1,5 +1,5 @@
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plugins {
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kotlin("jvm") version "1.4.31"
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kotlin("jvm") version "1.4.32"
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}
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group = "ru.mipt.npm"
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2
gradle/wrapper/gradle-wrapper.properties
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2
gradle/wrapper/gradle-wrapper.properties
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distributionBase=GRADLE_USER_HOME
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distributionPath=wrapper/dists
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distributionUrl=https\://services.gradle.org/distributions/gradle-6.7.1-bin.zip
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distributionUrl=https\://services.gradle.org/distributions/gradle-6.8.3-bin.zip
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zipStoreBase=GRADLE_USER_HOME
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zipStorePath=wrapper/dists
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@ -3,12 +3,12 @@ package lesson2
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class SimpleClass(val a: Int, val b: Double, c: Double)
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data class DataClass(val a: Int, val b: Double){
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val c get() = b +1
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data class DataClass(val a: Int, val b: Double) {
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val c get() = b + 1
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}
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fun main() {
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val simple = SimpleClass(1,2.0,3.0)
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val simple = SimpleClass(1, 2.0, 3.0)
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println(simple)
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34
src/main/kotlin/lesson4/Idiom31.kt
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34
src/main/kotlin/lesson4/Idiom31.kt
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package lesson4
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class Bad{
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val value: Int
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init {
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value = requestValue()
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}
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private fun requestValue(): Int = TODO()
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}
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//Factory functions are preferred to the initialization logic
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class Good internal constructor(val value: Int){
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init {
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//Initialization block is there to check arguments
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require(value >= 0)
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}
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companion object
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}
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private fun requestValue(): Int = TODO()
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// This is the factory-function
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fun Good() = Good(requestValue())
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// additional constructor-like builders could be added to the companion
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@OptIn(ExperimentalUnsignedTypes::class)
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fun Good.Companion.build(value: UInt) = Good(value.toInt())
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18
src/main/kotlin/lesson4/idiom27.kt
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18
src/main/kotlin/lesson4/idiom27.kt
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package lesson4
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import kotlin.random.Random
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//TODO move to beginning of the course
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fun main() {
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val b = Random.nextBoolean()
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// assign value to an expression
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val a = if (b) 0 else 1
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//Use Try/catch as an exception
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val result = try {
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"22a".toInt()
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} catch (e: NumberFormatException) {
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null //Strongly discouraged in performance-critical code
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}
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}
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src/main/kotlin/lesson4/idiom28.kt
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11
src/main/kotlin/lesson4/idiom28.kt
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package lesson4
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@OptIn(ExperimentalStdlibApi::class)
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fun main() {
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//Consume mutating lambda
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val list = buildList {
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repeat(10){
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add(it)
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}
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}
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}
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src/main/kotlin/lesson4/idiom29.kt
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12
src/main/kotlin/lesson4/idiom29.kt
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package lesson4
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import java.nio.file.Files
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import java.nio.file.Paths
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fun main() {
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val stream = Files.newInputStream(Paths.get("/some/file.txt"))
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// The resource is automatically closed when leaving the scope
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stream.buffered().reader().use { reader ->
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println(reader.readText())
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}
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}
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24
src/main/kotlin/lesson4/idiom30.kt
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24
src/main/kotlin/lesson4/idiom30.kt
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package lesson4
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interface Factory<T : Any> {
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fun build(str: String): T
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}
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class IntContainer(val arg: Int) {
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companion object : Factory<IntContainer> {
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override fun build(str: String) = IntContainer(str.toInt())
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}
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}
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class DoubleContainer(val arg: Double) {
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companion object : Factory<DoubleContainer> {
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override fun build(str: String) = DoubleContainer(str.toDouble())
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}
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}
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fun <T : Any> buildContainer(str: String, factory: Factory<T>): T = factory.build(str)
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fun main() {
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buildContainer("22", IntContainer)
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}
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17
src/main/kotlin/lesson4/idiom32.kt
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17
src/main/kotlin/lesson4/idiom32.kt
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package lesson4
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class ClassWithALazyProperty{
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//Use lazy delegate for something that should be calculated ones on first call
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val lazyValue by lazy {
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//Do dome heavy logic here
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}
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}
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//Using other delegates
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fun main() {
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val map = mapOf("a" to 1, "b" to 2)
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val a by map
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println(a)
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}
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36
src/main/kotlin/lesson4/idiom33.kt
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36
src/main/kotlin/lesson4/idiom33.kt
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package lesson4
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/**
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* The demonstration of use of inline [forEach] function with non-local return
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*/
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fun foo() {
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listOf(1, 2, 3, 4, 5).forEach {
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if (it == 3) return // non-local return directly to the caller of foo()
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print(it)
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}
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println("this point is unreachable")
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}
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/**
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* Definition of inline function
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*/
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inline fun List<Int>.forEachOdd(block: (Int) -> Unit) = forEach {
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if (it % 2 == 1) block(it)
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}
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/**
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* Using inline function for type reification during the compile time
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*/
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inline fun <reified T: Any> List<T>.prettyPrint() = forEach {
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when (T::class) {
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Double::class -> println("Double: ${it as Double}")
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Int::class -> println("Int: ${it as Int}")
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else -> it.toString()
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}
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}
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/**
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* **WARNING** inline functions are an advanced feature and should be used only for reification or non-local return
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* NOT for optimization.
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*/
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16
src/main/kotlin/lesson4/idiom34.kt
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16
src/main/kotlin/lesson4/idiom34.kt
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package lesson4
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/**
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* Values are boxed. Each call is indirect
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*/
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val list: List<Double> = List(20){it.toDouble()}
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/**
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* Still boxed
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*/
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val genericArray: Array<Double> = Array(20){it.toDouble()}
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/**
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* Non-boxed
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*/
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val specializedArray: DoubleArray = DoubleArray(20){it.toDouble()}
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