[Haskell-beginners] How does forever works ?

[Olivier Revollat]

>From what I understand, this code

main = forever $ do
  putStrLn "OK !"

is equivalent to this one :

main = do
  putStrLn "OK !"
  main

In the second case, it's a simple recursion, so far so good ... but when I
look at the implementation of "forever" i can't wrap my head around :

http://hackage.haskell.org/package/base-4.11.1.0/docs/src/Control.Monad.html#forever

forever <http://hackage.haskell.org/package/base-4.11.1.0/docs/src/Control.Monad.html#forever>
a <http://hackage.haskell.org/package/base-4.11.1.0/docs/src/Control.Monad.html#local-6989586621679327090>
  = let a' <http://hackage.haskell.org/package/base-4.11.1.0/docs/src/Control.Monad.html#local-6989586621679327091>
= a <http://hackage.haskell.org/package/base-4.11.1.0/docs/src/Control.Monad.html#local-6989586621679327090>
*> <http://hackage.haskell.org/package/base-4.11.1.0/docs/src/GHC.Base.html#%2A%3E>
a' <http://hackage.haskell.org/package/base-4.11.1.0/docs/src/Control.Monad.html#local-6989586621679327091>
in a' <http://hackage.haskell.org/package/base-4.11.1.0/docs/src/Control.Monad.html#local-6989586621679327091>

How does this works ? How does this make an infinite loop ?

I understand that *> discard his right argument but it doesn't help me
understand how forever implement an infinite loop ...
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