update book code

eBook/exercises/chapter_7/magnify_slice.go

@@ -0,0 +1,25 @@
+package main
+
+import "fmt"
+
+var s []int
+
+func main() {
+	s = []int{1, 2, 3}
+	fmt.Println("The length of s before enlarging is:", len(s))
+	fmt.Println(s)
+	s = enlarge(s, 5)
+	fmt.Println("The length of s after enlarging is:", len(s))
+	fmt.Println(s)
+}
+
+func enlarge(s []int, factor int) []int {
+	ns := make([]int, len(s) * factor)
+	// fmt.Println("The length of ns  is:", len(ns))
+	copy(ns, s)
+	//fmt.Println(ns)
+	s = ns
+	//fmt.Println(s)
+	//fmt.Println("The length of s after enlarging is:", len(s))
+	return s
+}