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 10 package main 11 12 // Send the sequence 2, 3, 4, ... to channel 'ch'. 13 func 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'. 21 func 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. 31 func 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 43 func main() { 44 Sieve() 45 } 46
