Type Conversion

Converting Between Numeric Types

Go never implicitly converts between numeric types, even ones that seem compatible like int and float64 -- you must convert explicitly using TargetType(value) syntax. This strictness catches bugs where precision could be silently lost.

Example: Converting Between Numeric Types

package main

import "fmt"

func main() {
	var i int = 10
	var f float64 = float64(i) / 3
	fmt.Println("as float:", f)
}

Truncation with Narrowing Conversions

Converting from a larger numeric type to a smaller one (like int to int8) doesn't raise an error if the value doesn't fit -- it silently truncates or wraps around, which can introduce subtle bugs if the source value is out of range.

Note: Always check whether a value fits before converting to a smaller type, to avoid silent data loss.

Example: Truncation with Narrowing Conversions

package main

import "fmt"

func main() {
	var big int = 300
	var small int8 = int8(big)
	fmt.Println("300 truncated to int8:", small)
}

String to Number with strconv

Converting a string like "42" into an actual number isn't a type conversion in Go's sense -- it requires the strconv package's parsing functions, such as strconv.Atoi, which can fail (e.g. on non-numeric input) and therefore return an error alongside the result.

Note: Always check the error returned by strconv functions before using the parsed value.

Example: String to Number with strconv

package main

import (
	"fmt"
	"strconv"
)

func main() {
	n, err := strconv.Atoi("42")
	if err != nil {
		fmt.Println("conversion failed:", err)
		return
	}
	fmt.Println("parsed number:", n+8)
}

Number to String

Going the other way, converting a number into its textual representation also uses strconv, typically strconv.Itoa for ints, rather than a plain string(n) conversion, which would misleadingly convert the number to a single Unicode character instead.

Example: Number to String

package main

import (
	"fmt"
	"strconv"
)

func main() {
	score := 95
	text := strconv.Itoa(score)
	fmt.Println("score as text: \"" + text + "\"")
}