Referential transparency example

rt.sc

// Referential transparency
// An value can be replaced by its definition without changing semantics

// Not RT
def foo() = {
  (println("hi"), println("hi"))
}
// bar() != foo()
def bar() = {
  val x = println(hi)
  (x, x)
}

// Is RT
def fooIO: (IO[Unit], IO[Unit]) = {
  (IO(println("hi")), IO(println("hi")))
}
// barIO == fooIO
def barIO: (IO[Unit], IO[Unit]) = {
  val x = IO(println(hi))
  (x, x)
}