github.com/MangoDowner/go-gm@v0.0.0-20180818020936-8baa2bd4408c/test/sieve.go (about)

     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  }