if as an expression in Scala

if/else evaluates to a value in Scala, so it can be assigned straight to a val.

val elevationGain = 820

// if/else is an expression, so it can be assigned to a val.
val grade =
  if elevationGain < 300 then "easy"
  else if elevationGain < 900 then "moderate"
  else "strenuous"

// Both branches must agree on a type; here both are Int.
def restStops(gain: Int): Int =
  if gain > 600 then 2 else 1

// Scala has no ternary operator because if already gives a value.
def waterLiters(hikers: Int, hot: Boolean): Double =
  val perPerson = if hot then 2.0 else 1.25
  hikers * perPerson

def hikePlan(): Unit =
  println(s"$grade, ${restStops(elevationGain)} rest stops")
  println(waterLiters(4, hot = true))

How it works

1. val grade = takes the result of an if elevationGain < 300 then "easy" chain that ends in else "strenuous".
2. def restStops(gain: Int): Int returns a one-line if gain > 600 then 2 else 1, where both branches are Int.
3. Inside waterLiters the local val perPerson = if hot then 2.0 else 1.25 shows why Scala needs no ternary operator.

Keywords and builtins used here

• Boolean
• Double
• Int
• Unit
• def
• else
• hikePlan
• if
• restStops
• then
• val
• waterLiters

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Step 1 of 3 in Expressions, step 4 of 27 in Language basics.

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