Returning New State

Compute the next state instead of mutating.

NewStateLabel.scala

object Main {
  def main(args: Array[String]): Unit = {
    val deposit = 
    val balance = 100
    val newBalance = balance + deposit
    val state = if (newBalance > balance) "grew" else "same"

    println("balance=" + balance)
    println("newBalance=" + newBalance)
    println("state=" + state)
  }
}

object Main {
  def main(args: Array[String]): Unit = {
    val deposit = 
    val balance = 100
    val newBalance = balance + deposit
    val state = if (newBalance > balance) "grew" else "same"

    println("balance=" + balance)
    println("newBalance=" + newBalance)
    println("state=" + state)
  }
}

object Main {
  def main(args: Array[String]): Unit = {
    val deposit = 
    val balance = 100
    val newBalance = balance + deposit
    val state = if (newBalance > balance) "grew" else "same"

    println("balance=" + balance)
    println("newBalance=" + newBalance)
    println("state=" + state)
  }
}

new-state-label Rather than mutating a variable, immutable code computes a new value and a label describing the change. The original value stays available for comparison.