Add named field construction #16

i-am-tom · 2019-09-27T13:52:49Z

The named library seems to make a lot of this look much prettier, so I'm very excited about this change!

Hoping @neongreen can give this change a quick look before I commit it to master :)

i-am-tom · 2019-09-27T13:53:20Z

Ah, need to fix the docs...

The `named` library seems to make a lot of this look much prettier, so I'm very excited about this change!

int-index · 2019-09-28T19:58:20Z

src/Data/Generic/HKD/Named.hs

+instance Append (S1 m h) t (S1 m h :*: t)
+instance Append x y z => Append (w :*: x) y (w :*: z)
+
+class Rearrange (i :: Type -> Type) (o :: Type -> Type) | i -> o


Why is this a class if it has no methods? Shouldn't it be a type family?

type family Rearrange (i :: Type -> Type) = (o :: Type -> Type) where ...

int-index · 2019-09-28T19:59:06Z

src/Data/Generic/HKD/Named.hs

+import GHC.Generics
+import Named ((:!), NamedF (..))
+
+class Append (xs :: Type -> Type) (ys :: Type -> Type) (zs :: Type -> Type)


Why is this a class if it has no methods? Shouldn't it be a type family?

type family Append (xs :: Type -> Type) (ys :: Type -> Type) = (zs :: Type -> Type) where ...

Good point; I think I'd set off with the intention of making this much more interestingly injective, but got lazy a bit too quick 😅

int-index · 2019-09-28T20:00:30Z

src/Data/Generic/HKD/Named.hs

+--
+-- >>> :{
+-- data User
+--   = User { name :: String, age :: Int, likesDogs :: Bool }


Shouldn't the example use fields of the same type but with different names to follow the motivation above?

Good point, probably clearer!

int-index · 2019-09-28T20:02:42Z

src/Data/Generic/HKD/Named.hs

+-- ... standing for ...("name" :! f [Char])
+-- ...   -> ("age" :! f Int) -> ("likesDogs" :! f Bool) -> HKD User f...
+-- ...
+class Record (structure :: Type) (f :: Type -> Type) (k :: Type)


The third parameter here can be replaced with an associated type.

The errors are never as useful, though :/

I'd be interested in exploiting some stuckness eventually to have an error if one forgets the type application, but it's probably out-of-scope for this change, so I'll leave it as-is :)

int-index · 2019-09-28T20:03:59Z

src/Data/Generic/HKD/Named.hs

+  grecord fill = \(Arg inner) -> fill (M1 (K1 inner))
+
+instance (GRecord right f structure k, rec ~ Rec0 x)
+    => GRecord (S1 ('MetaSel ('Just name) i d c) rec :*: right) f structure (name :! x -> k) where


There's no other instance matching on :*:, so better type errors / type inference is possible if the instance is defined as

left ~ ... => GRecord (left :*: right) f structure ...

Quite right; I'd intended for this behaviour to be introduced straight to Build.hs for any named-field record, but (having discussed with @kcsongor) the generic-lens upcasting doesn't work with unnamed fields yet, so it got split out. Good spot - I hadn't gone back and tidied up carefully enough 😇

int-index · 2019-09-28T20:06:26Z

In general, this looks great, thanks for taking the time to make higgledy work with named! I left a few suggestions based on my belief that type families are slightly nicer than functional dependencies for type-level computation, but these suggestions are all minor and safe to ignore.

neongreen · 2019-09-28T17:24:49Z

README.md

@@ -72,7 +75,7 @@ data User
  deriving (Generic, Show)

 user :: User
-user = User "Tom" 25 True
+user = User "Tom" 26 True


neongreen · 2019-09-28T18:31:12Z

README.md

@@ -184,13 +187,30 @@ eg7 = eg6 [1] [] ["Tom", "Tim"]
 -- Triple [1] [] ["Tom","Tim"]
 ```

+Should we need to work with records, we can exploit the label trickery of the
+[`named`](http://hackage.haskell.org/package/named) package. The `record`


Suggested change

[`named`](http://hackage.haskell.org/package/named) package. The `record`

[`named`](https://hackage.haskell.org/package/named) package. The `record`

neongreen · 2019-09-28T18:31:34Z

README.md

+eg8 = record @User
+
+eg9 :: HKD User Maybe
+eg9 = eg8 ! #name (Just "Tom") ! #likesDogs (Just True) ! #age (Just 26)


Perhaps break this into several lines?

i-am-tom

Thanks so much @int-index for taking a look, some really great spots :) I'll commit, push, bump versions, and close up!

i-am-tom · 2019-09-29T20:56:53Z

src/Data/Generic/HKD/Named.hs

+import GHC.Generics
+import Named ((:!), NamedF (..))
+
+class Append (xs :: Type -> Type) (ys :: Type -> Type) (zs :: Type -> Type)


Good point; I think I'd set off with the intention of making this much more interestingly injective, but got lazy a bit too quick 😅

i-am-tom · 2019-09-29T20:57:06Z

src/Data/Generic/HKD/Named.hs

+instance Append (S1 m h) t (S1 m h :*: t)
+instance Append x y z => Append (w :*: x) y (w :*: z)
+
+class Rearrange (i :: Type -> Type) (o :: Type -> Type) | i -> o


i-am-tom · 2019-09-29T20:58:22Z

src/Data/Generic/HKD/Named.hs

+--
+-- >>> :{
+-- data User
+--   = User { name :: String, age :: Int, likesDogs :: Bool }


Good point, probably clearer!

i-am-tom · 2019-09-29T20:59:57Z

src/Data/Generic/HKD/Named.hs

+-- ... standing for ...("name" :! f [Char])
+-- ...   -> ("age" :! f Int) -> ("likesDogs" :! f Bool) -> HKD User f...
+-- ...
+class Record (structure :: Type) (f :: Type -> Type) (k :: Type)


The errors are never as useful, though :/

I'd be interested in exploiting some stuckness eventually to have an error if one forgets the type application, but it's probably out-of-scope for this change, so I'll leave it as-is :)

i-am-tom · 2019-09-29T21:01:06Z

src/Data/Generic/HKD/Named.hs

+  grecord fill = \(Arg inner) -> fill (M1 (K1 inner))
+
+instance (GRecord right f structure k, rec ~ Rec0 x)
+    => GRecord (S1 ('MetaSel ('Just name) i d c) rec :*: right) f structure (name :! x -> k) where


Quite right; I'd intended for this behaviour to be introduced straight to Build.hs for any named-field record, but (having discussed with @kcsongor) the generic-lens upcasting doesn't work with unnamed fields yet, so it got split out. Good spot - I hadn't gone back and tidied up carefully enough 😇

@neongreen

Thanks @neongreen and @int-index!

neongreen · 2019-10-19T13:17:21Z

@i-am-tom ping

neongreen · 2019-10-20T20:25:18Z

Thanks!

Can you also ping me when a new version is up on Hackage?

i-am-tom · 2019-10-21T09:58:09Z

Ping :)

Thanks so much for your incredible patience - it has been a hectic few weeks, and your nudges are appreciated!

Add named field construction

049af74

The `named` library seems to make a lot of this look much prettier, so I'm very excited about this change!

i-am-tom force-pushed the named branch from 54ce050 to 049af74 Compare September 27, 2019 14:03

i-am-tom mentioned this pull request Sep 27, 2019

Allow 'build' with named fields #15

Closed

int-index reviewed Sep 28, 2019

View reviewed changes

neongreen reviewed Sep 28, 2019

View reviewed changes

i-am-tom commented Sep 29, 2019

View reviewed changes

Code review changes

ba5fc87

Thanks @neongreen and @int-index!

int-index approved these changes Sep 29, 2019

View reviewed changes

i-am-tom merged commit e3b2cc2 into master Oct 19, 2019

i-am-tom deleted the named branch October 19, 2019 17:09

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Add named field construction #16

Add named field construction #16

i-am-tom commented Sep 27, 2019

i-am-tom commented Sep 27, 2019

int-index Sep 28, 2019

i-am-tom Sep 29, 2019

int-index Sep 28, 2019

i-am-tom Sep 29, 2019

int-index Sep 28, 2019

i-am-tom Sep 29, 2019

int-index Sep 28, 2019

i-am-tom Sep 29, 2019

int-index Sep 28, 2019

i-am-tom Sep 29, 2019

int-index commented Sep 28, 2019 •

edited

neongreen Sep 28, 2019

neongreen Sep 28, 2019

neongreen Sep 28, 2019

i-am-tom Sep 29, 2019

i-am-tom left a comment

i-am-tom Sep 29, 2019

i-am-tom Sep 29, 2019

i-am-tom Sep 29, 2019

i-am-tom Sep 29, 2019

i-am-tom Sep 29, 2019

neongreen commented Oct 19, 2019

neongreen commented Oct 20, 2019

i-am-tom commented Oct 21, 2019 •

edited

	[`named`](http://hackage.haskell.org/package/named) package. The `record`
	[`named`](https://hackage.haskell.org/package/named) package. The `record`

Add named field construction #16

Add named field construction #16

Conversation

i-am-tom commented Sep 27, 2019

i-am-tom commented Sep 27, 2019

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

int-index commented Sep 28, 2019 • edited

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

i-am-tom left a comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

neongreen commented Oct 19, 2019

neongreen commented Oct 20, 2019

i-am-tom commented Oct 21, 2019 • edited

int-index commented Sep 28, 2019 •

edited

i-am-tom commented Oct 21, 2019 •

edited