cheat.sheets/sheets/_scala/Variables

// variable
// mutable
var x = 5

// value
// immutable, evaluated once during compilation
// GOOD
val x = 5
// BAD
x = 5

// lazy value
// immutable, evaluated once but only when called
lazy val x = 5

// definition
// immutable, evaluated every time it is called
def x = 5

// explicit type
val x: Double = 5