if Expressions

@main def weather(): Unit =
  val temperature = 18

  if temperature > 25 then
    println("It is hot")
  else if temperature > 15 then
    println("It is pleasant")
  else
    println("It is cold")

It is pleasant

Scala 3 writes if condition then ... else ..., with no parentheses needed. (The Scala 2 style, if (temperature > 25) { ... }, still works.)

if returns a value

In Scala, if is an expression: it produces a value. There's no separate ternary operator — you don't need one:

@main def status(): Unit =
  val age = 20
  val status = if age >= 18 then "adult" else "minor"
  println(status)

  val fee = if age < 12 then 5 else if age < 65 then 12 else 8
  println(s"Ticket: $$$fee")

adult
Ticket: $12

($$ in an s string prints a literal dollar sign.)

Using if as an expression works naturally with val: the value is decided once and never changes.

Common mistakes

• Leaving out the else when you use the result. Without else, the missing branch produces () (Unit), so the value's type becomes Any or Unit — rarely what you want.

Practice

Given an age, produce "adult" for 18 and over, "teen" for 13 to 17, and "child" otherwise, as a single val.

@main def ageGroup(): Unit =
  val age = 15
  val group =
    if age >= 18 then "adult"
    else if age >= 13 then "teen"
    else "child"
  println(group)

teen