On Wed, Dec 24, 2003 at 10:39:33AM +0000, Graham Klyne wrote:
It now seems to me that (some?) Monads are kinds of Functors, generalized to handle the "no value" case, and also composition.
This also had me thinking about sequence: is there a generalization to arbitrary monads that rearranges the monadic structure?
Perhaps looking into Category Theory could be enlightening for both of us - terms Monad and Functor where both taken from there.
11 and 18. If you define an instance of Monad for ((->) e) then
return (putStrLn "Hello!") 'x'
is a proper IO () value. Probably still not sensible ;)
Ah, I think I see your point. It would apply where monads are "nested", right?
Exactly.
Special treatment of 'return' could be helpful, but I am afraid that it could also make it look special, like a return keyword in C.
I certainly wouldn't argue for special treatment _in the language_, but OTOH, I think it might be helpful if compiler diagnostics hinted at the possibility when a type error is detected in a form like return x y.
Agreed. Best regards, Tom -- .signature: Too many levels of symbolic links