good good study, day day up!

vendor/gopl.io/ch8/pipeline3/main.go

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+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 231.
+
+// Pipeline3 demonstrates a finite 3-stage pipeline
+// with range, close, and unidirectional channel types.
+package main
+
+import "fmt"
+
+//!+
+func counter(out chan<- int) {
+	for x := 0; x < 100; x++ {
+		out <- x
+	}
+	close(out)
+}
+
+func squarer(out chan<- int, in <-chan int) {
+	for v := range in {
+		out <- v * v
+	}
+	close(out)
+}
+
+func printer(in <-chan int) {
+	for v := range in {
+		fmt.Println(v)
+	}
+}
+
+func main() {
+	naturals := make(chan int)
+	squares := make(chan int)
+
+	go counter(naturals)
+	go squarer(squares, naturals)
+	printer(squares)
+}
+
+//!-