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1 Comparison Operators

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

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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?

go
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?

go
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?

go
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?

go
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?

go
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.