add: slices advanced ops

16-slices/questions/5-slice-others-wip.md

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+full slice exp
+make
+copy
+
+# Slice Internals Quiz
+
+## Where does a slice value stores its elements?
+1. In the global backing array that is shared by all the slices
+2. In a separate backing array that a slice value points to *CORRECT*
+3. In the slice value itself (like an array)
+
+> **1:** There isn't something called the global backing array.
+> 
+> **2:** That's right. A slice doesn't store any elements direcly. It points to an array that is stored separately on the computer memory, and a slice points to that array, a slice is just a window to that array.
+> 
+> **3:** A slice values doesn't store any elements by itself. It's just a description of its backing array.
+
+
+## What's a backing array?
+1. An array of trustworthy friends that you can count on always
+2. An array that is stored in the slice value
+3. A slice value stores its elements in it *CORRECT*
+
+> **1:** Oh, come on!
+> 
+> **2:** Nope, a slice value doesn't store its backing array, the slice value just points to it. The backing array is stored separately from the slice value.
+
+
+## What does this program print?
+```go
+nums := []int{10, 15, 10, 2, 3, 4}
+digits := nums[len(nums)-3:]
+
+nums[len(nums)-1] = 8
+digits[0] += nums[3]
+
+fmt.Println(digits)
+```
+1. [2 3 4]
+2. [4 3 4]
+3. [4 3 8] *CORRECT*
+4. [10 15 10]
+5. [4 15 8]
+
+> **3:** Awesome! At first, digits is [2 3 4]. After `nums[len(nums)-1] = 8`, the digits becomes [2 3 8] (it's because, digits is created by slicing the nums slice, so they share the same backing array). And lastly, after `digits[0] += nums[3]`, the digits becomes [4 3 8].
+
+
+## Find the correct explanation below
+1. A slice variable can store a slice value and the slice value is actually a slice header behind the scenes *CORRECT*
+2. A slice variable can only store the same slice value and it cannot be changed afterward
+3. A slice header stores the slice value
+
+> **1:** That's right. You can change the slice values that is being stored in a slice variable, and the slice value is actually a slice header behind the scenes.
+> 
+> **3:** Nope, actually a slice header and a slice value is the same thing.
+
+
+* after slicing, does it copy all the values to the new slice?
+* why indexing a slice is fast? (array is contagious on memory)
+* separate backing arrays question
+* sliced array share the same explicit array
+
+## 
+backing array
+slice header
+capacity
+append mechanics