On 21 Dec 2011, at 14:07, Erik Hesselink <hessel...@gmail.com> wrote:
On Wed, Dec 21, 2011 at 14:10, Bas van Dijk <v.dijk....@gmail.com>
wrote:
The semantics of Maybe are
clear: it's failure-and-prioritized-choice.
Are you sure?
Yes.
There are (at least) four Monoid instances for Maybe
[1]. With a direct instance for Maybe and its Dual you have only
covered two.
Types don't just give data a representation: types evoke structure.
The data stored by Maybe can be made into a monoid in several ways,
but the failure-management role of Maybe makes just one of them
appropriate.
Cheers
Conor
Erik
[1] https://byorgey.wordpress.com/2011/04/18/monoids-for-maybe/
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