learngo/11-if/questions/1-comparison-operators.md

Which one below is not one of the equality operators of Go?

1. ==
2. !=
3. > CORRECT

3: That's the greater operator. It checks whether an ordered value is greater than the other or not.

Which one below is not one of the ordering operators of Go?

1. >
2. <=
3. == CORRECT
4. <

3: That's the equal operator. In an expression, it checks whether a value (operand) is equal to another value (operand).

Which one of these types is returned by the comparison operators?

1. int
2. byte
3. bool CORRECT
4. float64

3: That's right. All the comparison operators return an untyped bool value (true or false).

Which one of these below cannot be used as an operand to ordering operators (>, <, >=, <=)?

1. int value
2. byte value
3. string value
4. bool value CORRECT
5. all of them

1-2: This is an ordered value, it can be used.

3: String is an ordered value because it's a series of numbers. So, it can be used as an operand.

4: That's right. A bool value is not an ordered value, so it cannot be used with ordering operators.

Which one of these cannot be used as an operand to equality operators (==, !=)?

1. int value
2. byte value
3. string value
4. bool value
5. They all can be used CORRECT

5: That's right. Every comparable value can be used as an operand to equality operators.

What does this code print?

fmt.Println("go" != "go!")
fmt.Println("go" == "go!")

1. true true
2. true false CORRECT
3. false true
4. false false
5. error

3-4: Watch out for the exclamation mark at the end of the second string value.

What does this code print?

fmt.Println(1 == true)

1. true
2. 1
3. false
4. 2
5. error CORRECT

5: That's right. A numeric constant cannot be compared to a bool value.

What does this code print?

fmt.Println(2.9 > 2.9)
fmt.Println(2.9 <= 2.9)

1. true true
2. true false
3. false true CORRECT
4. false false
5. error

What does this code print?

fmt.Println(false >= true)
fmt.Println(true <= false)

1. true true
2. true false
3. false true
4. false false
5. error CORRECT

5: That's right. Bool values are not ordered values, so they cannot be compared using the comparison operators.

How to fix this program without losing precision?

package main
import "fmt"

func main() {
    weight, factor := 500, 1.5
    weight *= factor

    fmt.Println(weight)
}

1. It cannot be fixed
2. weight *= float64(factor)
3. weight *= int(factor)
4. weight = float64(weight) * factor
5. weight = int(float64(weight) * factor) CORRECT

1: It can be fixed.

2: Type mismatch: weight is int.

3: Lost precision: factor will be 1.

4: Type mismatch: weight is int (cannot assign back).

5: That's right. The result would be 750.