[Haskell-cafe] Confusion on the third monad law when using lambda abstractions

Jake McArthur jake.mcarthur at gmail.com
Thu Jun 18 14:35:20 EDT 2009

Hans van Thiel wrote:
> Just to show I'm paying attention, there's an arrow missing, right?
>        (.)   ::            (b  ->  c) -> (a ->   b) -> (a ->   c)

Correct. I noticed that after I sent it but I figured that it would be 

I also used (>>>) where I meant (>=>) at the bottom. They are 
semantically the same, of course, but (>>>) requires the Kleisli newtype. :(

> Many thanks, also to the others who've replied. I've wondered about
> (=<<) usage for a long time too, and this is all very illuminating. I'll
> work this through and put it in my monad tutorial, if I may (without
> implicating you guys in any way, of course, unless you insist...)

You're welcome. I do not insist on anything either way. ;)

- Jake

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