39368.scala

// To demonstrate different ways of pattern matching, let's consider the
// following example case class and instance:
case class Person(name: String, age: Int)
val ada = Person("Ada", 36)

// Run using `sbt "runMain ed.patternMatching"`.
@main def patternMatching =
  // There are several ways to pattern match on the `ada` instance:
  // 1. Pattern matching on the case class constructor using `Person(name, age)`.
  //    If the pattern matches, the value of `n` is bound `ada.name` field, and
  //    `a` is bound to the `ada.age` field.
  ada match
    case Person(n, a) => println(f"$n is $a years old")

  // 2. We can also check only that `ada` is of type `Person` without binding its
  //    fields by using a `:` pattern. The `:` pattern is used to check if a value is
  //    of a certain type.
  ada match
    case p: Person => println(f"${p.name} is ${p.age} years old")

  // 3. If we want to both bind the fields and bind a value to the whole instance,
  //    we can use an `@` pattern.
  ada match
    case p @ Person(n, a) => println(f"${p.name} is ${a} years old")