What is the difference between the = and := operator?

The = and := operators are used for variable assignment in Go, but they have different purposes and behaviors:

  1. Assignment Operator =:
    • The = operator is used for variable assignment in Go.
    • It assigns the value on the right-hand side to the variable on the left-hand side.
    • It can be used to assign a new value to an existing variable or declare and initialize a new variable.
    • When used with an existing variable, it updates the value of that variable.

Example:

package main

import "fmt"

func main() {
    var x int
    x = 42         // Assign a value to the variable x

    y := 10        // Declare and initialize a new variable y
    y = y + 5      // Update the value of the variable y
    fmt.Println(x, y)
}
  1. Short Variable Declaration := Operator:
    • The := operator is a short variable declaration specific to Go.
    • It is used to declare and initialize a new variable within a limited scope.
    • Unlike the = operator, it can only be used for variable declaration and initialization, not for updating an existing variable’s value.
    • The short variable declaration is only valid inside functions and can’t be used at the package level.

Example:

package main

import "fmt"

func main() {
    // Short variable declaration to declare and initialize a variable
    x := 42

    // This will cause a compile-time error because the variable x is already declared
    // x := 10

    fmt.Println(x)
}

In the example above, x := 42 uses the short variable declaration to declare and initialize the variable x within the main() function.

To summarize, the = operator is used for variable assignment and can both initialize a new variable and update an existing one. The := operator is used for short variable declaration and initialization within a limited scope, and it cannot be used to update the value of an existing variable.

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