Declaring Variables

Using the var keyword

var varName type = value

Variables declared without an explicit initial value receive their zero value.

• Either type, value, or both must be specified:

  var name string = "John"  // explicit type and value
  var surname = "Doe"       // type inferred as string
  var age int16             // explicit type, zero value (0)

• Multiple variables in a single line, same or different types:

  var name, age = "John", 30  // mixed types, inferred
  var a, b, c int = 1, 2, 3   // all must match the declared type
  var x, y int                // both zero value (0)

• Grouped declaration:

  var (
  	name    string = "John"
  	surname        = "Doe"  // inferred as string
  	age     int             // zero value (0)
  )

Using the := syntax

varName := value

• Multiple variables in a single line:

  name, age := "John", 30

  Re-declaration of a variable in the same scope is not allowed.

  BUT

  If at least one identifier on the left side is new, this syntax is allowed.

  x := 10
  
  x := 20 // <-- compiler: no new variables on left side of :=
  
  x, y := 20, 30 // y is new, so this is allowed
  
  fmt.Println(x, y) // 20 30

  New identifiers are declared and existing ones are reassigned.

Using the const keyword

Constants are fixed values that cannot change after declaration.

const varName type = value

• Constants declaration may omit the type but must include a value:

  const daysInWeek int = 7  // explicit type and value
  const hoursInDay = 24     // type is inferred as int

• Grouped declaration:

  const (
  	daysInWeek = 7
  	hoursInDay = 24
  )