hello world for channels

concurrency/channels/go.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"fmt"
+)
+
+func sum(a []int, c chan int) {
+	s := 0
+	for _, v := range a {
+		s += v
+	}
+	c <- s
+}
+
+func main() {
+	a := []int{7, 2, 8, -9, 4, 0}
+	c := make(chan int)
+	go sum(a[:len(a)/2], c)
+	go sum(a[len(a)/2:], c)
+	go sum(a, c)
+	x, y, z := <-c, <-c, <-c
+	fmt.Printf("%d %d %d\n", x, y, z)
+
+	// panics with deadlock if buffer doesn't match reads from chan
+	// throw: all goroutines are asleep - deadlock!
+	c2 := make(chan int, 2)
+	c2 <- 1
+	c2 <- 2
+	// must not do this without increasing buffer size: c2 <- 2
+	fmt.Println(<-c2)
+	fmt.Println(<-c2)
+
+	// note that this chanel is buffered, and that we don't need to launch go 
+	// routines
+	c_buffered := make(chan int, 10)
+	sum(a[:len(a)/2], c_buffered)
+	sum(a[len(a)/2:], c_buffered)
+	sum(a, c_buffered)
+	x, y, z = <-c_buffered, <-c_buffered, <-c_buffered
+	fmt.Printf("%d %d %d\n", x, y, z)
+}