_content/talks/2014/hellogophers/sieve_20090925.go

// +build ignore,OMIT

package main

import "fmt"

// Send the sequence 2, 3, 4, ... to channel 'ch'.
func generate(ch chan<- int) {
	for i := 2; ; i++ {
		ch <- i;	// Send 'i' to channel 'ch'.
	}
}

// Copy the values from channel 'in' to channel 'out',
// removing those divisible by 'prime'.
func filter(src <-chan int, dst chan<- int, prime int) {
	for i := range src {	// Loop over values received from 'src'.
		if i%prime != 0 {
			dst <- i;	// Send 'i' to channel 'dst'.
		}
	}
}
// BREAK OMIT
// The prime sieve: Daisy-chain filter processes together.
func sieve() {
	ch := make(chan int);  // Create a new channel.
	go generate(ch);       // Start generate() as a subprocess.
	for {
		prime := <-ch;
		fmt.Print(prime, "\n");
		ch1 := make(chan int);
		go filter(ch, ch1, prime);
		ch = ch1;
	}
}

func main() {
	sieve();
}