add: exercises and quiz for appending and slicing

x-tba/slices/exercises/README.md

@@ -1,11 +1,6 @@
 # Slice Exercises
 
 ## TODO
-* slicing
-  * slice exercises... n:m.. using len etc..
-  * create a pagination
-  * use the same slice variable
-
 * internals
   * shared array: implicit/explicit
   * appending to a nil array

x-tba/slices/questions/3-slicing.md

@@ -1,57 +0,0 @@
-# Slicing Quiz
-
-## What does this program print?
-```go
-nums := []int{9, 7, 5}
-nums = append(nums, 2, 4, 6)
-
-fmt.Println(nums[2:4])
-```
-1. [9 7 5 2 4 6]
-2. [5 2] *CORRECT*
-3. [4 6]
-4. [7 2]
-
-> **2:** nums is [9 7 5 2 4 6]. So, nums[2:4] is [5 2]. Remember, in nums[2:4] -> 2 is the starting index, so nums[2] is 5; And 4 is the stopping position, so nums[4-1] is 2 (-1 because the stopping position is the element position not an index). So, nums[2:4] returns a new slice that contains the elements at the middle of the nums slice.
-
-
-## What does this program print?
-```go
-names := []string{"einstein", "rosen", "newton"}
-fmt.Println(names[:])
-```
-1. [einstein rosen newton] *CORRECT*
-2. [einstein rosen]
-3. [einstein]
-4. []
-
-> **1:** The start index's default value is 0, and the stop position's default value is the length of the slice. So, `names[:]` equals to `names[0:3]`. It returns a new slice with the same elements.
-
-
-## How can you get "rosen" element?
-```go
-names := []string{"einstein", "rosen", "newton"}
-names2 := names[1:len(names) - 1]
-```
-1. names2[0] *CORRECT*
-2. names2[1]
-3. names2[2]
-
-> **1:** That's right: names2 is ["rosen"] after the slicing.
-> 
-> **2:** That's not right. names is ["einstein" "rosen" "newton"] but names2 is ["rosen"] after the slicing. So, names2[1] is an error, it's because, the length of the names2 is 1.
-
-
-## What does this program print?
-```go
-names := []string{"einstein", "rosen", "newton"}
-names = names[1:]
-names = names[1:]
-fmt.Println(names)
-```
-1. [einstein rosen newton]
-2. [rosen newton]
-3. [newton] *CORRECT*
-4. []
-
-> **3:** Remember, slicing returns a new slice. Here, each slicing statement overwrites the names slice with the newly returned slice from the slicing. At first, the names was [einstein rosen newton. After the first slicing, the names becomes [rosen newton]. After the second slicing, names becomes [newton]. See this for the complete explanation: https://play.golang.org/p/EsEHrSeByFR