Hello Olivier,

On Mon, Jul 09, 2018 at 01:31:07PM +0200, Olivier Revollat wrote:

> 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 a = let a' = a *> a' in a'

`*>` is the same as `>>` (if you have ever met `>>`), with the difference

that the latter works on monads only. In do notation, we could write

forever :: Monad m => m a -> m b

forever a = let a' = do a

a' in

do a'

Which should be easier to get: we `do` a'; a' is nothing but a and a',

so we do a and then a', which is nothing but a and a', etc.

Does this explanation feel right?

As soon as you can, familiarise yourself what the do notation desugars to:

in my opinion plain operators are clearer

-F

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