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

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?

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