add: slice internals exercises

x-tba/slices/exercises/README.md

@@ -1,55 +1,68 @@
 # Slice Exercises
 
-## TODO
-* internals
-  * shared array: implicit/explicit
-  * appending to a nil array
-  * sorts package sorting
+---
 
-  * exercises about capacity
-  * exercises about the mechanics of append
-    * growing
-    * adding elements at the middle etc
-  * exercises about full slice expressions
+# ANNOUNCEMENT
 
-  * questions:
-    * slice header questions
-    * slice and ask what's the pointer field, len, cap etc
-    * when a new backing array is allocated: nil, empty, no capacity
-    * when to use a full slice expression
+I teach you what the other courses don't even care to teach. 
 
+**What's new?**
+* New Section: Advanced Slice Operations
+* New Exercises for the Slice Internals
+* New Exercises for the Slices: Advanced Operations
+
+**What are you going to learn?**
+* Full Slice Expressions: Limiting access to the backing array
+* Make(): Preallocation
+* Copy(): Efficiently and safely copy elements without using a loop
+* Multi-Dimensional Slices
+
+**What's coming next?**
+* Empty Filer Finder: Your first taste of file operations.
+* Bouncing Ball: Create a bouncing ball animation on a 2D surface.
+* Png Parser: Parse a PNG file by hand and tell its dimensions.
+
+These lectures will be added in the next 3 weeks.
+
+**Statistics:**
+* +1 hour of additional content!
+* +5 new lectures
+* +20 new questions
+* 3 + ? new exercises
+
+**Total content in the slices section:**
+* ? hours
+* ? lectures
+* ? questions
+* ? exercises
 
 ---
 
-## Exercises Level I - Basics
+## Full Slice Exp + Make + Copy + Multi-Dim Slices
 
-1. **[???](https://github.com/inancgumus/learngo/tree/master/16-slices/exercises/???)**
+# FIX THIS
+1. **[Limit the backing array sharing](https://github.com/inancgumus/learngo/tree/master/16-slices/exercises/??-limit-the-backing-array-sharing)**
 
----
-2. **[Get and Set Array Elements](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/02-get-set-arrays)**
+* fix the excess memory allocation
+  * return a huge slice from a func, ask the student fix it
+* full slice exp: https://play.golang.org/p/SPrLspRBXdI
+* copy: https://play.golang.org/p/SPrLspRBXdI
+  * + put \n for the beatles exercise using copy
+  ```go
+    s = append(s, 0 /* use the zero value of the element type */)
+    copy(s[i+1:], s[i:])
+    s[i] = x
+  ```
 
-3. **[Refactor to Array Literals](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/03-array-literal)**
 
-4. **[Refactor to Ellipsis](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/04-ellipsis)**
+* multi dim slices batches
+```go
+actions := []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
+batchSize := 3
+var batches [][]int
 
-5. **[Fix](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/05-fix)**
-
-6. **[Compare the Arrays](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/06-compare)**
-
-7. **[Assign the Arrays](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/07-assign)**
-
----
-
-## Exercises Level II
-
-1. **[Wizard Printer](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/08-wizard-printer)**
-
-2. **[Currency Converter](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/09-currency-converter)**
-
-3. **[Hipster's Bookstore Search Engine](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/10-hipsters-love-search)**
-
-4. **[Find the Average](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/11-average)**
-
-5. **[Number Sorter](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/12-sorter)**
-   
-6. **[Word Finder](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/13-word-finder)**
+for batchSize < len(actions) {
+    actions, batches = actions[batchSize:], append(batches, actions[0:batchSize:batchSize])
+}
+batches = append(batches, actions)
+```

x-tba/slices/exercises/_template/main.go

@@ -0,0 +1,14 @@
+package main
+
+// ---------------------------------------------------------
+// EXERCISE: ?
+//
+//
+//
+// EXPECTED OUTPUT
+//
+//
+// ---------------------------------------------------------
+
+func main() {
+}

x-tba/slices/exercises/_template/solution/main.go

@@ -0,0 +1,11 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+func main() {
+}

x-tba/slices/exercises/fix-xx-limit-the-backing-array-sharing/api/api.go

@@ -0,0 +1,20 @@
+package api
+
+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`.
+func Read(start, stop int) []int {
+	// ----------------------------------------
+	// RESTRICTIONS — ONLY ADD YOUR CODE HERE
+
+	portion := temps[start:stop]
+
+	// ----------------------------------------
+	return portion
+}
+
+// All returns all the temperature readings
+func All() []int {
+	return temps
+}

x-tba/slices/exercises/fix-xx-limit-the-backing-array-sharing/main.go

@@ -0,0 +1,73 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"fmt"
+
+	"github.com/inancgumus/learngo/16-slices/exercises/19-limit-the-backing-array-sharing/api"
+)
+
+// ---------------------------------------------------------
+// EXERCISE: Limit the backing array sharing
+//
+//  You've created an API that returns population counts in a country.
+//  To do that, you return an int slice up to some portion of it.
+//
+//  There is a program that uses your API but it appends to the slice
+//  that your API returns. Doing so, overwrites your API's slice's
+//  backing array as well.
+//
+//  Change your API so that it prevents the overwriting when
+//  the client code wants to append to the returned slice from your
+//  API.
+//
+//
+// STEPS
+//
+//   1. Open the code inside the `api/api.go` folder
+//
+//   2. Fix the code there (not here — but run this code after)
+//
+//
+// CURRENT OUTPUT
+//
+//       The following program overwrites the elements incorrectly
+//          You need to change your API to prevent this behavior
+//                           ^ ^
+//                           | |
+//   API's readings: [5 10 3 1 3 80 90]
+//   Your readings : [5 10 3 1 3]
+//
+//
+// EXPECTED OUTPUT
+//
+//   Now the program cannot change the API's original backing array
+//  (beyond the returned capacity) (so the api now owns the control)
+//                           ^  ^
+//                           |  |
+//   API's readings: [5 10 3 25 45 80 90]
+//   Your readings : [5 10 3 1 3]
+//
+// ---------------------------------------------------------
+
+func main() {
+	// DO NOT TOUCH THE FOLLOWING CODE
+	// THIS IS THE CLIENT PROGRAM THAT USES YOUR API
+	// YOU CANNOT CONTROL IT! :)
+
+	// reads the first three temperatures
+	temps := api.Read(0, 3)
+
+	// appends two new temperature readings
+	temps = append(temps, []int{1, 3}...)
+
+	// prints the current temperatures
+	fmt.Println("API's readings:", api.All())
+	fmt.Println("Your readings :", temps)
+}

x-tba/slices/exercises/fix-xx-limit-the-backing-array-sharing/solution/api/api.go

@@ -0,0 +1,24 @@
+package api
+
+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`.
+func Read(start, stop int) []int {
+	// Uses a full slice expression to control the length of the
+	// backing array (or the capacity of the returned slice).
+	//
+	// So the next append allocates a new backing array, which
+	// in turn doesn't overwrite the temps slice's backing array.
+	//                           ^^
+	//                           ||
+	//                          /  \
+	//                         |    |
+	portion := temps[start:stop:stop]
+	return portion
+}
+
+// All returns all the temperature readings
+func All() []int {
+	return temps
+}

x-tba/slices/exercises/fix-xx-limit-the-backing-array-sharing/solution/main.go

@@ -0,0 +1,23 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"fmt"
+
+	"github.com/inancgumus/learngo/16-slices/exercises/19-limit-the-backing-array-sharing/solution/api"
+)
+
+func main() {
+	temps := api.Read(0, 3)
+
+	temps = append(temps, []int{1, 3}...)
+
+	fmt.Println("API's readings:", api.All())
+	fmt.Println("Your readings :", temps)
+}