update book code

eBook/exercises/chapter_7/map_function.go

@@ -0,0 +1,32 @@
+package main
+
+import "fmt"
+
+func main() {
+	list := []int{0, 1, 2, 3, 4, 5, 6, 7}
+	mf := func(i int) int {
+		return i * 10
+	}
+	/*
+	result := mapFunc(mf, list)
+	for _, v := range result {
+		fmt.Println(v)
+	}
+	*/
+	println()
+	// shorter:
+	fmt.Printf("%v", mapFunc(mf, list) )
+}
+
+func mapFunc(mf func(int) int, list []int) ([]int) {
+	result := make([]int, len(list))
+	for ix, v := range list {
+		result[ix] = mf(v)
+	}
+	/*
+	for ix := 0; ix<len(list); ix++ {
+		result[ix] = mf(list[ix])
+	}
+	*/
+	return result
+}