Type conversion

Learn explicit type conversion in Go.

Type conversion

Go doesn't mix different number types on its own; adding an int and a float64 is a compile error. Conversion is written explicitly as Type(value):

adet := 3
fiyat := 12.5
toplam := float64(adet) * fiyat   // 37.5
tam := int(toplam)                // 37 (fraction dropped)

An int() conversion doesn't round; it cuts off the fraction.

Number and text conversion

string(65) gives the character with code 65 ("A"), not "65". To turn numbers into text and text into numbers use the strconv package:

s := strconv.Itoa(42)        // "42"
n, err := strconv.Atoi("17")  // 17, nil
_, err = strconv.Atoi("on")   // error: invalid syntax

Because Atoi can return an error, its result is always checked.

Exercise Compute an average

Declare toplam := 17 and adet := 4. Compute the average with a float64 conversion and print it with fmt.Printf("%.2f\n", ortalama).

Show example solution

package main

import "fmt"

func main() {
    toplam := 17
    adet := 4
    ortalama := float64(toplam) / float64(adet)
    fmt.Printf("%.2f\n", ortalama)
}

Test yourself

What is <code>int(9.99)</code>?
- An error
- 9
- 10
- 9.99
Show answer

9 — Converting a decimal to an integer truncates toward zero; use math.Round to round.

Convert to decimal

ortalama := ____(toplam) / float64(adet)

Show answer

ortalama := float64(toplam) / float64(adet)

Conversion and result

float64(3)

3.0
int(7.8)

7
strconv.Itoa(5)

"5"
string(rune(65))

"A"

Next lesson: Type definitions

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