Example
class Person(val name: String, var age: Int)
val john = new Person(“John”, 30)
val judy = new Person(“Judy”, 55)
val sum1 = sumOfAges(john, judy)
john.age += 1 // birthday
val sum2 = sumOfAges(john, judy)
// sum1 != sum2
Referential transparency violated
Passing identical
objects!
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