Go Type Casting#

Type casting is the process of converting the value of one data type (integer, float, string) to another data type. For example,

// variable of float type
var floatValue float = 9.8

// convert float to int
var intValue int = int(floatValue)

Here, int(floatValue) specifies that we are converting the float value 9.8 to 9.

Since we are manually performing the type conversion, this is called explicit type casting in Go.

#Go Explicit Type Casting

Golang provides various predefined functions like int(), float32(), string(), etc to perform explicit type casting.

Let's see some of the examples of explicit type casting:

#Example: Go float to int conversion

package main
import "fmt"

func main() {

  var floatValue float32 = 5.45

  // type conversion from float to int
  var intValue int = int(floatValue)

  fmt.Printf("Float Value is %g\n", floatValue)
  fmt.Printf("Integer Value is %d", intValue)
}

Output

Float Value is 5.45
Integer Value is 5

Here, we have used the function int() to convert the value from 5.45 to 5.

In this case, we are manually converting the type of one type to another. Hence, it is called explicit type casting.

#Example: Go int to float conversion

package main
import "fmt"

func main() {

  var intValue int = 2

  // type conversion from int to float
  var floatValue float32 = float32(intValue)


  fmt.Printf("Integer Value is %d\n", intValue)
  fmt.Printf("Float Value is %f", floatValue)

}

Output

Integer Value is 2
Float Value is 2.000000

Here, we have used the function float32() to convert an integer value to float. The integer value 2 changed to 2.000000 after the type casting.

#Implicit Type Casting in Go

In implicit type casting, one data type is automatically converted to another data type. However, Go doesn't support implicit type casting. For example,

package main
import "fmt"

func main() {

  // initialize integer variable to a floating-point number
  var number int = 4.34

  fmt.Printf("Number is %g", number)
}

In the above example, we have created an int type variable named number. Here, we are trying to assign a floating point value 4.34 to the int variable.

When we run this program, we will get an error:

./prog.go:8:7: constant 4.34 truncated to integer

This is because Golang doesn't support implicit type conversion.

#Example: Add int and float number using Go type casting

package main
import "fmt"

func main() {

  var number1 int = 20
  var number2 float32 = 5.7
  var sum float32

  // addition of different data types
  sum = float32(number1) + number2

  fmt.Printf("Sum is %g",sum)
}

Output

Sum is 25.7

In the above example, we have created an integer variable named number1 and a float variable named number2. Notice the line,

sum = float32(number1) + number2

Here, we are adding values of two different types (float and int). Since Go doesn't support implicit type casting, we need to change the value of one type to another.

This is why we have used float32(number1) to convert the int type variable number to float type.