Values, Variables, and Types

Values

val x: Int = 42

• val means immutable.

  It's like const or final in other language.

• Int is optional, but it's recommended.

  The compiler can infer that the type of variable is Int.

Variables

var aVariable: Int = 4
aVariable = 5

• var defines variable.

  We can assign a new value to it.

  Changing Variables is side effects in functional programming.

In functional programming, we prefer Values over Variable because Values are immutable, and they won't cause side effects.

Types

• Boolean

  It only has 2 values, true or false.

• Char, String

  Char is the single character. It's written between the single quotes.

  val aChar: Char = 'c'
  

• Int, Short, Long

  They all represent the number.

  Short presents 2 btyes, 16 bits, 2¹⁶.

  Int presents 4 btyes, 32 bits, 2³².

  Long presents 8 btyes, 64 bits, 2⁶⁴.

• Double

  It represents float number.

• Unit

  It's void in other languages.

  Side effect is an expression that returns Unit.