用kotlin协程管道求质数

Question

https://blog.csdn.net/yangxjs...
哪位大佬能解释一下，以下代码的思路为什么和上面链接中的思路对不上，这段代码怎样理解？filter到底是怎样过滤质数的？

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

fun main() = runBlocking {//sampleStart
    var cur = numbersFrom(2)
    for (i in 1..10) {
        val prime = cur.receive()
        println(prime)
        cur = filter(cur, prime)
    }
    coroutineContext.cancelChildren() // 取消所有的子协程, 让 main 函数结束//sampleEnd
}

fun CoroutineScope.numbersFrom(start: Int) = produce<Int> {
    var x = start
    while (true)
        send(x++) // 从 start 开始递增的无限整数流
}

fun CoroutineScope.filter(numbers: ReceiveChannel<Int>, prime: Int) = produce<Int> {
    for (x in numbers)
        if (x % prime != 0)
            send(x)
}