Source file doc/progs/sieve1.go

// 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

import "fmt"

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

// Filter out input values divisible by 'prime', send rest to returned channel
func filter(in chan int, prime int) chan int {
    out := make(chan int)
    go func() {
        for {
            if i := <-in; i%prime != 0 {
                out <- i
            }
        }
    }()
    return out
}

func sieve() chan int {
    out := make(chan int)
    go func() {
        ch := generate()
        for {
            prime := <-ch
            out <- prime
            ch = filter(ch, prime)
        }
    }()
    return out
}

func main() {
    primes := sieve()
    for {
        fmt.Println(<-primes)
    }
}