Zero value

Zero value of a variable in Golang refers to the value it contains till it is not explicitly initialized. Zero value may also be referred as default value of a variable.

A zero value is provided by the compiler in order to allocate space in memory for the variable after it is declared.
This zero value is different for a variable of different data types.
Example, for a variable of bool type, the zero value is false; for integers, it is 0 etc. Thus, below code will print 0.

package main

import "fmt"

func main(){
   var int num
   fmt.Println(num)
}

Zero value only exists till the variable is not provided a value. Also, below code snippets are equivalent.

var num int
var num int = 0

var flag bool
var flag bool = false

var name string
var name string = ""

Below table provides a quick reference to the zero value for each data type.

Data Type Zero Value
int 0
float32 0
float64 0
bool false
string “”
pointers nil
functions nil
slices nil
channels nil
maps nil
interfaces nil

An uninitialized array will contain all the elements with the zero value of the type of array. Example,

var arr[5] int
fmt.Print(arr)

will print [0,0,0,0,0] since the zero value of int(which is the data type of array) is 0.

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