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// $G $F.go && $L $F.$A  # don't run it - goes forever

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

// 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(in <-chan int, out chan<- int, prime int) {
        for {
                i := <-in // Receive value of new variable 'i' from 'in'.
                if i%prime != 0 {
                        out <- i // Send 'i' to channel 'out'.
                }
        }
}

// 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
                print(prime, "\n")
                ch1 := make(chan int)
                go Filter(ch, ch1, prime)
                ch = ch1
        }
}

func main() {
        Sieve()
}