good good study, day day up!

vendor/gopl.io/ch5/squares/main.go

@@ -0,0 +1,30 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 135.
+
+// The squares program demonstrates a function value with state.
+package main
+
+import "fmt"
+
+//!+
+// squares returns a function that returns
+// the next square number each time it is called.
+func squares() func() int {
+	var x int
+	return func() int {
+		x++
+		return x * x
+	}
+}
+
+func main() {
+	f := squares()
+	fmt.Println(f()) // "1"
+	fmt.Println(f()) // "4"
+	fmt.Println(f()) // "9"
+	fmt.Println(f()) // "16"
+}
+
+//!-