02-arithmetic-operators.md

Lab: Arithmetic Operators

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See also Arithmetic Operators in the Go manual.

All the code fragments in this lab are complete mini-programs, so you can paste them into the editor and run them to see the results:

Running the code fragments

1. Right click in Explorer pane to create a new file, e.g. test.go
2. Paste the question code snippet into the editor pane
3. Open the terminal window and execute go run test.go
4. Re-use your test.go file by replacing the content with that of the next question.

Questions

1. What would be the output of the following code -

   package main
   
   import "fmt"
   
   func main() {
           var a string = "one"
           var b int = 2
           fmt.Print(a + b)
   }

   • Error
   • 2one
   • 3
   • one2

   Reveal

   Error

   The program would not compile due to strict type checking performed by the compiler. You cannot add int with string.

2. What would be the output of the following code -

   package main
   
   import "fmt"
   
   func main() {
           var a float64 = 5.9
           var b int = 2
           fmt.Print(a + b)
   }

   • Error
   • 7.9
   • 7
   • 7.0

   Reveal

   Error

   The program would not compile due to strict type checking performed by the compiler. Whilst both varaibles are numeric types, the compiler will not do implict type casts. You could fix it with an explicit type cast

   fmt.Print(a + float64(b))

   ...then the answer would be 7.9

3. What would be the output of the following code -

   package main
   
   import "fmt"
   
   func main() {
           var a float64 = 5.9
           a++
           fmt.Print(a)
   }

   • 5
   • 7.0
   • 6
   • 6.9

   Reveal

   6.9

   ++ is the increment operator. It adds 1 to any numeric variable. a++ is equivalent to a = a + 1

4. What would be the output of the following code -

   package main
   
   import "fmt"
   
   func main() {
           var a int = 10
           a--
           fmt.Print(a)
   }

   • 10
   • 9
   • 11
   • Error

   Reveal

   9

   -- is the decrement operator. It subtracts 1 from any numeric variable. a-- is equivalent to a = a - 1

5. What would be the output of the following code -

   package main
   
   import "fmt"
   
   func main() {
           var a, b float64 = 24.4, 3.0
           fmt.Println(a / b)
           fmt.Println(int(a) % int(b))
   }

   • 8.133333333333333
     0
   • 9.001333333333333
     0
   • 8.00
     0.11
   • 8.2
     ERROR

   Reveal

   8.133333333333333
   0

   The first operation is a straight division of two floats, so it will produce a float result.

   In the second operation, the floats are first casted to ints so the values become 24 and 3. Then a modulo division is performed %. Modulo yields the remainder when the value on the left is divided by the value on the right. Remember from elementary level maths - 24 divided by 3 = 8 remainder 0.