1// build 2 3// Copyright 2009 The Go Authors. All rights reserved. 4// Use of this source code is governed by a BSD-style 5// license that can be found in the LICENSE file. 6 7// Test basic concurrency: the classic prime sieve. 8// Do not run - loops forever. 9 10package main 11 12// Send the sequence 2, 3, 4, ... to channel 'ch'. 13func Generate(ch chan<- int) { 14 for i := 2; ; i++ { 15 ch <- i // Send 'i' to channel 'ch'. 16 } 17} 18 19// Copy the values from channel 'in' to channel 'out', 20// removing those divisible by 'prime'. 21func Filter(in <-chan int, out chan<- int, prime int) { 22 for { 23 i := <-in // Receive value of new variable 'i' from 'in'. 24 if i%prime != 0 { 25 out <- i // Send 'i' to channel 'out'. 26 } 27 } 28} 29 30// The prime sieve: Daisy-chain Filter processes together. 31func Sieve() { 32 ch := make(chan int) // Create a new channel. 33 go Generate(ch) // Start Generate() as a subprocess. 34 for { 35 prime := <-ch 36 print(prime, "\n") 37 ch1 := make(chan int) 38 go Filter(ch, ch1, prime) 39 ch = ch1 40 } 41} 42 43func main() { 44 Sieve() 45} 46