Proposal: Add a wrapped applicative type to Data.Monoid

I see this as being generally (as in, to the users of Haskell as a whole) useful: newtype Ap f a = Ap { getAp :: f a } deriving (Applicative, Eq, Foldable, Functor, Generic, Generic1 ,Monad, Ord, Read, Show, Traversable) Some hand-written instances: instance (Applicative f, Semigroup a) => Semigroup (Ap f a) where (Ap x) <> (Ap y) = Ap $ liftA2 (<>) x y instance (Applicative f, Monoid a) => Monoid (Ap f a) where mempty = Ap $ pure mempty

+1 from me. I've written this type at least a dozen times in various
projects.
On Tue, Mar 27, 2018 at 10:22 AM, Daniel Cartwright
I see this as being generally (as in, to the users of Haskell as a whole) useful:
newtype Ap f a = Ap { getAp :: f a } deriving (Applicative, Eq, Foldable, Functor, Generic, Generic1 ,Monad, Ord, Read, Show, Traversable)
Some hand-written instances: instance (Applicative f, Semigroup a) => Semigroup (Ap f a) where (Ap x) <> (Ap y) = Ap $ liftA2 (<>) x y
instance (Applicative f, Monoid a) => Monoid (Ap f a) where mempty = Ap $ pure mempty
_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries
-- -Andrew Thaddeus Martin

I proposed same thing some time ago. The main point of contention was the
name. I hope you have better luck!
On Tue, Mar 27, 2018, 10:23 AM Daniel Cartwright
I see this as being generally (as in, to the users of Haskell as a whole) useful:
newtype Ap f a = Ap { getAp :: f a } deriving (Applicative, Eq, Foldable, Functor, Generic, Generic1 ,Monad, Ord, Read, Show, Traversable)
Some hand-written instances: instance (Applicative f, Semigroup a) => Semigroup (Ap f a) where (Ap x) <> (Ap y) = Ap $ liftA2 (<>) x y
instance (Applicative f, Monoid a) => Monoid (Ap f a) where mempty = Ap $ pure mempty _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

I can definitely see "App" as being overloaded (Application).
Good names that I see are "Ap" and "Apply".
I think "Ap" is fine.
On Tue, Mar 27, 2018, 10:28 AM David Feuer
I proposed same thing some time ago. The main point of contention was the name. I hope you have better luck!
On Tue, Mar 27, 2018, 10:23 AM Daniel Cartwright
wrote: I see this as being generally (as in, to the users of Haskell as a whole) useful:
newtype Ap f a = Ap { getAp :: f a } deriving (Applicative, Eq, Foldable, Functor, Generic, Generic1 ,Monad, Ord, Read, Show, Traversable)
Some hand-written instances: instance (Applicative f, Semigroup a) => Semigroup (Ap f a) where (Ap x) <> (Ap y) = Ap $ liftA2 (<>) x y
instance (Applicative f, Monoid a) => Monoid (Ap f a) where mempty = Ap $ pure mempty _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

One thing that I would like to respectfully point out - is that the
members' of this library mailing list end up derailing otherwise useful
conversations over the choice of a name, which is frankly a silly
bottleneck. I would much rather roll a die or flip a coin to choose a name,
and just get on to implementing the proposed thing, provided it is the case
that it is seen as generally useful.
On Tue, Mar 27, 2018 at 10:59 AM, Daniel Cartwright
I can definitely see "App" as being overloaded (Application). Good names that I see are "Ap" and "Apply".
I think "Ap" is fine. On Tue, Mar 27, 2018, 10:28 AM David Feuer
wrote: I proposed same thing some time ago. The main point of contention was the name. I hope you have better luck!
On Tue, Mar 27, 2018, 10:23 AM Daniel Cartwright
wrote: I see this as being generally (as in, to the users of Haskell as a whole) useful:
newtype Ap f a = Ap { getAp :: f a } deriving (Applicative, Eq, Foldable, Functor, Generic, Generic1 ,Monad, Ord, Read, Show, Traversable)
Some hand-written instances: instance (Applicative f, Semigroup a) => Semigroup (Ap f a) where (Ap x) <> (Ap y) = Ap $ liftA2 (<>) x y
instance (Applicative f, Monoid a) => Monoid (Ap f a) where mempty = Ap $ pure mempty _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

+1 to add it.
I don't care one way or the other about the name. =)
-Edward
On Tue, Mar 27, 2018 at 11:06 AM, Daniel Cartwright
One thing that I would like to respectfully point out - is that the members' of this library mailing list end up derailing otherwise useful conversations over the choice of a name, which is frankly a silly bottleneck. I would much rather roll a die or flip a coin to choose a name, and just get on to implementing the proposed thing, provided it is the case that it is seen as generally useful.
On Tue, Mar 27, 2018 at 10:59 AM, Daniel Cartwright
wrote:
I can definitely see "App" as being overloaded (Application). Good names that I see are "Ap" and "Apply".
I think "Ap" is fine. On Tue, Mar 27, 2018, 10:28 AM David Feuer
wrote: I proposed same thing some time ago. The main point of contention was the name. I hope you have better luck!
On Tue, Mar 27, 2018, 10:23 AM Daniel Cartwright
wrote: I see this as being generally (as in, to the users of Haskell as a whole) useful:
newtype Ap f a = Ap { getAp :: f a } deriving (Applicative, Eq, Foldable, Functor, Generic, Generic1 ,Monad, Ord, Read, Show, Traversable)
Some hand-written instances: instance (Applicative f, Semigroup a) => Semigroup (Ap f a) where (Ap x) <> (Ap y) = Ap $ liftA2 (<>) x y
instance (Applicative f, Monoid a) => Monoid (Ap f a) where mempty = Ap $ pure mempty _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries
_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

So it's settled, we have an `Ed` type.
On Wed, Mar 28, 2018, 2:51 AM Edward Kmett
+1 to add it.
I don't care one way or the other about the name. =)
-Edward
On Tue, Mar 27, 2018 at 11:06 AM, Daniel Cartwright
wrote:
One thing that I would like to respectfully point out - is that the members' of this library mailing list end up derailing otherwise useful conversations over the choice of a name, which is frankly a silly bottleneck. I would much rather roll a die or flip a coin to choose a name, and just get on to implementing the proposed thing, provided it is the case that it is seen as generally useful.
On Tue, Mar 27, 2018 at 10:59 AM, Daniel Cartwright < chessai1996@gmail.com> wrote:
I can definitely see "App" as being overloaded (Application). Good names that I see are "Ap" and "Apply".
I think "Ap" is fine. On Tue, Mar 27, 2018, 10:28 AM David Feuer
wrote: I proposed same thing some time ago. The main point of contention was the name. I hope you have better luck!
On Tue, Mar 27, 2018, 10:23 AM Daniel Cartwright
wrote: I see this as being generally (as in, to the users of Haskell as a whole) useful:
newtype Ap f a = Ap { getAp :: f a } deriving (Applicative, Eq, Foldable, Functor, Generic, Generic1 ,Monad, Ord, Read, Show, Traversable)
Some hand-written instances: instance (Applicative f, Semigroup a) => Semigroup (Ap f a) where (Ap x) <> (Ap y) = Ap $ liftA2 (<>) x y
instance (Applicative f, Monoid a) => Monoid (Ap f a) where mempty = Ap $ pure mempty _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries
_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries
_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries
participants (5)
-
Andrew Martin
-
Daniel Cartwright
-
David Feuer
-
Edward Kmett
-
Theodore Lief Gannon