AllThatIsWrongWithImperativeCode

Imperative.scala

// result is never used, can this line be removed?
val result = calculate(input)

update(input)

save(input.child)

foo()

// can the above four lines be re-arranged in a different order? 
// can foo even be deleted?

That you are required to know what calculate, update, save and foo do internally to be able to reason about this snippet of code is the point here. Such a thing would not be required in e.g.: Haskell.