update: slice exercises 23

16-slices/exercises/23-limit-the-backing-array-sharing/api/api.go

@@ -1,32 +1,21 @@
 package api
 
-// note: "client" means the users or importers of your package.
-
-// The original temperatures slice.
 var temps = []int{5, 10, 3, 25, 45, 80, 90}
 
-//                ^  ^   ^  ^           ^
-//                |  |   |  +-----------+
-// the client is allowed to |
-// change these elements.   |
-//                          |
-// but the client shouldn't change the
-// rest of the elements after the 3rd element.
-
-// Read returns a range of temperature readings beginning from
-// the `start` until to the `stop`.
+// Read returns a slice of elements from the temps slice.
 func Read(start, stop int) []int {
 	// ----------------------------------------
-	// RESTRICTIONS — ONLY ADD YOUR CODE HERE
+	// RESTRICTIONS — ONLY ADD YOUR CODE IN THIS AREA
 
-	// returns a slice from the temps slice to the client.
 	portion := temps[start:stop]
 
+	// RESTRICTIONS — ONLY ADD YOUR CODE IN THIS AREA
 	// ----------------------------------------
+
 	return portion
 }
 
-// All returns all the temperature readings
+// All returns the temps slice
 func All() []int {
 	return temps
 }

16-slices/exercises/23-limit-the-backing-array-sharing/main.go

@@ -16,38 +16,24 @@ import (
 // ---------------------------------------------------------
 // EXERCISE: Limit the backing array sharing
 //
-//  You've created a package and saved the temperatures in an int slice.
-//  (find it in the api folder).
+//  In this exercise: API means the api package. It's in the
+//  api folder.
 //
-//  When `Read()` function is called, you return the desired elements.
+//  `Read` function of the api package returns a portion of
+//  a slice. The main function [main()] below uses the
+//  Read function.
 //
-//  Another programmer has decided to use your package.
-//  She calls: `api.Read(0, 3)` and gets a slice with a length of 3.
+// `main()` appends to the slice but doing so changes the
+//  backing array of the api package's temps slice as well.
+//  We don't want that.
 //
-//  However: She appends to the slice, so she practically changes
-//  the elements in the api package's `temps` slice (the original one).
-//
-//  Only allow her to change the first three elements.
-//  Prevent her from changing the rest of the elements of
-//  `api.temps` slice.
+//  Only allow `main()` to change the part of the slice
+//  it receives from the Read function.
 //
 //
-// BE CAREFUL
+// NOTE
 //
-//   This code imports the api package from the learn go programming
-//   original repository. So, when you change the code in the api folder
-//   ensure that this code imports your own code.
-//
-//   see above (this is the original repository code):
-//   you need to change it to your own repository if you're using your own
-//   repository:
-//
-//   "github.com/inancgumus/learngo/16-slices/exercises/23-limit-the-backing-array-sharing/api"
-//
-//
-// STEPS
-//
-//   You only need to change the code inside the `api/api.go` folder
+//   You need to import the api package.
 //
 //
 // CURRENT
@@ -57,13 +43,14 @@ import (
 //   api.temps     : [5 10 3 1 3 80 90]
 //   main.temps    : [5 10 3 1 3]
 //                           ^ ^ append changes the api package's
-//                               temps slice: [1 3]
+//                               temps slice's backing array.
 //
 //
 //
 // EXPECTED
 //
-//   Now the program cannot change the API's original backing array.
+//   The corrected api package does not allow the `main()` change
+//   the api package's temps slice's backing array.
 //                           |  |
 //                           v  v
 //   api.temps     : [5 10 3 25 45 80 90]
@@ -72,17 +59,15 @@ import (
 // ---------------------------------------------------------
 
 func main() {
-	// DO NOT TOUCH THE FOLLOWING CODE
-	// THIS IS THE CLIENT PROGRAM THAT USES YOUR API
-	// YOU CANNOT CONTROL IT! :)
+	// DO NOT CHANGE ANYTHING IN THIS CODE.
 
 	// get the first three elements from api.temps
-	temps := api.Read(0, 3)
+	slice := api.Read(0, 3)
 
-	// changes the api.temps's backing array.
-	// you need to prevent this.
-	temps = append(temps, []int{1, 3}...)
+	// append changes the api package's temps slice's
+	// backing array as well.
+	slice = append(slice, []int{1, 3}...)
 
 	fmt.Println("api.temps     :", api.All())
-	fmt.Println("main.temps    :", temps)
+	fmt.Println("main.slice    :", slice)
 }

16-slices/exercises/23-limit-the-backing-array-sharing/solution/api/api.go

@@ -1,24 +1,22 @@
 package api
 
-// The original temperatures slice.
 var temps = []int{5, 10, 3, 25, 45, 80, 90}
 
-// Read returns a range of temperature readings beginning from
-// the `start` until to the `stop`.
+// Read returns a slice of elements from the temps slice.
 func Read(start, stop int) []int {
 	//
-	// This third index prevents the clients of this package from
-	// overwriting the original temps slice's backing array. It
-	// limits the capacity of the returned slice. See the
-	// full slice expressions lecture.
-	//                            ^
-	//                            |
+	// The third index prevents the `main()` from
+	// overwriting the original temps slice's
+	// backing array. It limits the capacity of the
+	// returned slice. See the full slice expressions
+	// lecture for more details.
+	//
 	portion := temps[start:stop:stop]
 
 	return portion
 }
 
-// All returns all the temperature readings
+// All returns the temps slice
 func All() []int {
 	return temps
 }

16-slices/exercises/23-limit-the-backing-array-sharing/solution/main.go

@@ -14,9 +14,10 @@ import (
 )
 
 func main() {
-	temps := api.Read(0, 3)
-	temps = append(temps, []int{1, 3}...)
+	slice := api.Read(0, 3)
+
+	slice = append(slice, []int{1, 3}...)
 
 	fmt.Println("api.temps     :", api.All())
-	fmt.Println("main.temps    :", temps)
+	fmt.Println("main.slice    :", slice)
 }