2014 Applicative => Monad proposal

Daniel Díaz Casanueva dhelta.diaz at gmail.com
Wed Jun 5 20:08:45 CEST 2013

Hi there!

I am excited about this proposal, and I really hopes it will be performed.
I have been following the discussion for a long time, always perceiving
that Applicative as a superclass of Monad is the right thing to do. As a
consequence, Functor will also be a superclass of Monad. This changes may
affect my code, but I will be glad to make any changes.

There is a wiki page related [1] that should be updated.

Also, I am wondering if our agreement to implement this proposal would
imply an Applicative class being included in a future Haskell Report.

Daniel Díaz.


[1] HaskellWiki: Functor-Applicative-Monad Proposal -

On Wed, Jun 5, 2013 at 6:00 PM, Conal Elliott <conal at conal.net> wrote:

> +1. Looks great. Thanks!
> On Thu, May 23, 2013 at 12:39 PM, David Luposchainsky <
> dluposchainsky at googlemail.com> wrote:
>> Hello libraries,
>> it's on! Time to tackle the Applicative-Monad issue, hopefully once and
>> for all. Over the last couple of weeks I've looked through previous
>> proposals, asked #haskell about their opinions, and compiled it all into
>> one file that sums up what I made of that. It's a bit long for an email
>> and uses markdown, so I'll just provide links at the end of this mail
>> instead of pasting it in here. In there, the whole thing and how to
>> approach it is explained in more detail. Here's an abstract of what it
>> the proposal consists of:
>> - Don't break compatibility
>> - Apply it gently
>> - Applicative m => Monad m
>> - Applicative into Prelude (and therefore into the Report)
>> - (Alternative m, Monad m) => MonadPlus m
>> - Promote `join` into the Monad typeclass
>> Let's make this happen! I'm going to give a ballpark discussion period
>> of four weeks, but since I can imagine this discussion could become
>> quite complex we shouldn't take it too serious. I'll summarize what's
>> been going on periodically though.
>> David
>> Links:
>> The proposal text on Github (link fixed, sorry for the deadlink
>> yesterday):
>> https://github.com/quchen/articles/blob/master/applicative_monad.md
>> (This file is subject to changes, depending on how this discussion goes.
>> I'll try to make it reflect the current consensus.)
>> And just in case Github silentbans me again for submitting too many
>> edits to my Gist (grrr), here's a copy of the file on HPaste as backup:
>> http://hpaste.org/88423
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