Arrays Quiz

What's the length of this array literal?

gadgets := [...]string{"Mighty Mouse", "Amazing Keyboard", "Shiny Monitor"}

1. 0
2. 1
3. 2
4. 3 CORRECT

4: Yes! There are 3 elements in the element list. So, Go sets the length of the array to 3.

What's the type and length of this array literal?

gadgets := [...]string{}

1. [0]string and 0 CORRECT
2. [0]string{} and 0
3. [1]string and 1
4. [1]string{} and 1

1: Yes! There are no elements in the element list. So, Go sets the length of the array to 0.

What does this program print?

package main
import "fmt"

func main() {
	gadgets := [3]string{"Confused Drone"}
	fmt.Printf("%q\n", gadgets)
}

1. [3]string{"Confused Drone", "", ""}
2. [1]string{"Confused Drone"}
3. ["Confused Drone" "" ""] CORRECT
4. ["Confused Drone"]

1: %q verb doesn't print the type of an array.

2, 4: Array's length cannot change depending on the elements.

3: Yes! Go sets the uninitialized elements to their zero values.

Are these arrays comparable?

gadgets := [3]string{"Confused Drone"}
gears   := [...]string{"Confused Drone"}

fmt.Println(gadgets == gears)

1. Yes, because they have identical types and elements
2. No, because their types are different CORRECT
3. No, because their elements are different

2: Yes! gadget's type is [3]string whereas gears's type is [1]string.

What does this program print?

gadgets := [3]string{"Confused Drone", "Broken Phone"}
gears   := gadgets

gears[2] = "Shiny Mouse"

fmt.Printf("%q\n", gadgets)

1. ["Confused Drone" "Broken Phone" "Shiny Mouse"]
2. ["Confused Drone" "Broken Phone" ""] CORRECT
3. ["" "" "Shiny Mouse"]
4. ["" "" ""]

2: Yes! When you assign an array, Go creates a copy of the original array. So, gadgets and gears arrays are not connected. Changing one of them won't effect the other one.

What's the type of the digits array?

digits := [...][5]string{
	{
		"## ",
		" # ",
		" # ",
		" # ",
		"###",
	},
	[5]string{
		"###",
		"  #",
		"###",
		"  #",
		"###",
	},
}

1. [...][5]string
2. [2][2]string
3. [2][5]string CORRECT
4. [5][5]string

3: Awesome! There are two inner arrays, so the outer array's length becomes 2. Also note that, [5]string in front of the second element is unnecessary.

What does this program print?

rates := [...]float64{
    5: 1.5,
    2.5,
    0: 0.5,
}

fmt.Printf("%#v\n", rates)

1. [7]float64{0.5, 0, 0, 0, 0, 1.5, 2.5} CORRECT
2. [7]float64{1.5, 2.5, 0.5, 0, 0, 0, 0}
3. [3]float64{1.5, 2.5, 0.5}
4. [3]float64{0.5, 2.5, 1.5}

1: That's right! For the explanation check out the example in the course repository here: https://github.com/inancgumus/learngo/tree/master/14-arrays/11-keyed-elements/06-keyed-and-unkeyed

Are these arrays equal?

type three [3]int

nums  := [3]int{1, 2, 3}
nums2 := three{1, 2, 3}

fmt.Println(nums == nums2)

Note: To solve this question you need to watch the comparison and unnamed types lectures.

1. Yes, because they have identical underlying types and elements CORRECT
2. No, because their types are different
3. No, because their length is different

1: Yes! They both have the same underlying types: [3]int

Are these array variables equal?

type (
    threeA [3]int
    threeB [3]int
)

nums  := threeA{1, 2, 3}
nums2 := threeA(threeB{1, 2, 3})

fmt.Println(nums == nums2)

Note: To solve this question you need to the watch comparison and unnamed types lectures.

1. Yes, because they have identical underlying types and elements CORRECT
2. No, because their types are different
3. No, because their length is different

1: Yes! Actually, arrays have different types, so normally they're not comparable. However, when you convert threeB{1, 2, 3} array to threeA type, they become comparable.