[Haskell-beginners] Understanding "Signals, Not Generators"

[Nathan Hüsken]

Hey

I am currently reading Signals, Not Generators". I am on page 10 where the phantom type era is introduced. I have trouble understanding because I do not understand how the system is to be used. Let us assume I have a signal and an action to print the output:

signal :: DSignal era Int
action :: Int -> Io ()
action = putStrLn . show

Now, I consume the signal:
reactive = consume signal action

=> reactive :: Reactive era (IO ())

And make an io action:

toIO reactive :: IO ()

My question is: what does this io action do?

Thanks!
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