Imported Upstream version 60upstream/60

1 files changed, 51 insertions, 0 deletions

diff --git a/doc/progs/sieve1.go b/doc/progs/sieve1.go
new file mode 100644
index 000000000..e1411a334
--- /dev/null
+++ b/doc/progs/sieve1.go
@@ -0,0 +1,51 @@
+// 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 i := 0; i < 100; i++ { // Print the first hundred primes.
+		fmt.Println(<-primes)
+	}
+}