Implementation of a prime sieve using a series of cascading Go channels building on each to filter out non-primes. From: http://play.golang.org/p/9U22NfrXeq

concPrimeSieve.go

package main

// A concurrent prime sieve
// from: http://play.golang.org/p/9U22NfrXeq

// 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 from 'in'.
        if i%prime != 0 {
            out <- i // Send 'i' to 'out'.
        }
    }
}

// The prime sieve: Daisy-chain Filter processes.
func main() {
    ch := make(chan int) // Create a new channel.
    go Generate(ch)      // Launch Generate goroutine.
    for i := 0; i < 10; i++ {
        prime := <-ch
        print(prime, "\n")
        ch1 := make(chan int)
        go Filter(ch, ch1, prime)
        ch = ch1
    }
}

I read about this idea so decided to write my own. (The one above works fine but this might be easier to follow.)

//` Generates prime numbers by creating a filter for each new prime found & adding
// it to the end of then chain. If a number makes it through then it is a prime!
func display_primes() {
                // Create generator for ints starting at the first prime (2)
                gen := make(chan int)               // channel that "generates" the integers
                go func() { for ii := 2; ; ii++ { gen <- ii } }()
 
                var end <-chan int = gen            // current end of chain of filters
                for {
                                prime := <-end                  // get next prime
                                fmt.Println(prime)              // display the prime
 
                                // Make a filter for this prime - go-routine with in/out channels
                                next := make(chan int)
                                go func(value int, src <-chan int, dst chan<- int) {
                                                for i := range src { if i%value > 0 { dst <- i } }
                                }(prime, end, next)
                                end = next
                }
}