Tour of Go (Concurrency) but in Kotlin Coroutines

concurrency_1.kt

import kotlinx.coroutines.*

suspend fun say(s: String) {
    for (i in 1..5) {
        delay(100L)
        println(s)
    }
}

fun main() = runBlocking {
    launch { say("world") }
    say("hello")
}

concurrency_2.kt

import kotlinx.coroutines.*
import kotlinx.coroutines.channels.*

suspend fun sum(s: List<Int>, c: Channel<Int>) {
    var sum = 0
    for (v in s) {
        sum += v
    }
    c.send(sum)
}

fun main() = runBlocking {
    val s = listOf(7, 2, 8, -9, 4, 0)
    
    val c = Channel<Int>()
    launch { sum(s.subList(s.size / 2, s.size - 1), c) }
    launch { sum(s.subList(0, s.size / 2), c) }
    
    val x = c.receive()
    val y = c.receive()
    
    println("$x + $y = ${x + y}")
}

concurrency_3.kt

import kotlinx.coroutines.*
import kotlinx.coroutines.channels.*

fun main() = runBlocking {
    val c = Channel<Int>(capacity = 2)
    c.send(1)
    c.send(2)
    println(c.receive())
    println(c.receive())
}

concurrency_4.kt

import kotlinx.coroutines.*
import kotlinx.coroutines.channels.*

suspend fun fibonacci(n: Int, c: Channel<Int>) {
    var x = 0
    var y = 1
    for (i in 0..<n) {
        c.send(x)
        val oldX = x
        x = y
        y = oldX + y
    }
    c.close()
}

fun main() = runBlocking {
    val cap = 10
    val c = Channel<Int>(capacity = cap)
    launch { fibonacci(cap, c) }
    for (i in c) {
        println(i)
    }
}

concurrency_5.kt

import kotlinx.coroutines.*
import kotlinx.coroutines.channels.*
import kotlinx.coroutines.selects.*

suspend fun fibonacci(c: Channel<Int>, quit: Channel<Int>) {
    var x = 0
    var y = 1
    var running = true
    while (running) {
        select<Unit> {
            c.onSend(x) { value ->
                val oldX = x
                x = y
                y = oldX + y
            }
            
            quit.onReceive { value ->
                println("quit")
                running = false
            }
        }
    }
}

fun main() = runBlocking {
    val c = Channel<Int>()
    val quit = Channel<Int>()
    launch {
        for (i in 0..<10) {
            println(c.receive())
        }
        quit.send(0)
    }
    fibonacci(c, quit)
}