[Haskell-cafe] Lazy patterns

Good day, I am trying to understand the lazy patterns as explained at https://www.haskell.org/tutorial/patterns.html If I type in the example without putting a ~ round the pattern sure enough I do not get an answer as the text says. What I completely fail to understand is why there is no CPU usage, increasing memory usage, stack overflow or other runtime error before I use ^C to stop it. What is going on under the hood ? Jon