Monad of no `return` Proposal (MRP): Moving `return` out of `Monad`

[Henrik Nilsson]

Hi all,

David Feuer wrote:

 > I take your concerns about unnecessary breaking changes seriously.
 > And it is certainly true that a large amount of existing code will
 > break. However, I am not at all convinced that the "mental weight" of
 > this change is nearly as great as that of the now-accomplished AMP,
 > in the presence of good error messages.

That may be true (and if pressed, I'd likely agree with you), but
it is beside the Graham and I were making: AMP does not necessitate
"monad of no return", and the cost of the additional breakage of
the latter should thus be justified in terms of how essential it is
for other reasons. At least there should be a very compelling
argument that the advantages clearly outweighs the costs. And again,
in any case like this, I think the burden of proof necessarily
rests with those who are arguing for the change.

 > I think removing error-prone redundancy is a good thing.

Undeniably. But does eliminating this particular
redundancy make enough of a practical difference to
justify the costs? There are plenty of opportunities
to break laws and introducing strictness bugs anyway.
See previous e-mail.

All the best,

/Henrik

-- 
Henrik Nilsson
School of Computer Science
The University of Nottingham
nhn at cs.nott.ac.uk




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