Promote and single Foldable, Traversable, Const, and Identity (#337)

* Promote and single Foldable, Traversable, Const, and Identity

This completes the `Data.Singletons.Prelude.*` changes necessary to
support `Monad` and friends. This:

* Adds the appropriate modules for the `Foldable` and `Traversable`
  classes, as well as the `Identity` and `Const` newtypes.
* Uncomments various things in
  `Data.Singletons.Prelude.{Applicative,Monad}` that couldn't be
  supported before due to the lack of the classes in the previous
  bullet points.
* Reexports the appropriate `Foldable`/`Traversable` functions from
  `Data.{Promotion,Singletons}.Prelude.List` to mirror what
  `Data.List` does. This required some reorganization of internal
  modules, but was otherwise straightforward.

Checks off the second bullet point in #184.

* Use list comprehensions in a couple more places

CHANGES.md

@@ -72,9 +72,17 @@ Changelog for singletons project
   `(%<>)`, as they are superseded by the corresponding methods from
   `PSemigroup` and `SSemigroup`.
 
-* Add promoted and singled versions of the `Functor`, `Applicative`,
-  `Alternative`, `Monad`, `MonadPlus`, and `MonadZip`. This grants the ability
-  to promote or single `do`-notation and list comprehensions.
+* Add promoted and singled versions of the `Functor`, `Foldable`,
+  `Traversable`, `Applicative`, `Alternative`, `Monad`, `MonadPlus`, and
+  `MonadZip` classes. Among other things, this grants the ability to promote
+  or single `do`-notation and list comprehensions.
+  * `Data.{Promotion,Singletons}.Prelude.List` now reexports more general
+    `Foldable`/`Traversable` functions wherever possible, just as `Data.List`
+    does.
+
+* Add `Data.{Promotion,Singletons}.Prelude.{Const,Identity}`, which define
+  promoted and singled version of the `Const` and `Identity` data types,
+  respectively.
 
 * Promote and single the `Down` newtype in `Data.Singletons.Prelude.Ord`.
 

singletons.cabal

@@ -77,12 +77,15 @@ library
                       Data.Singletons.Prelude.Applicative
                       Data.Singletons.Prelude.Base
                       Data.Singletons.Prelude.Bool
+                      Data.Singletons.Prelude.Const
                       Data.Singletons.Prelude.Either
                       Data.Singletons.Prelude.Enum
                       Data.Singletons.Prelude.Eq
+                      Data.Singletons.Prelude.Foldable
                       Data.Singletons.Prelude.Function
                       Data.Singletons.Prelude.Functor
                       Data.Singletons.Prelude.IsString
+                      Data.Singletons.Prelude.Identity
                       Data.Singletons.Prelude.Ord
                       Data.Singletons.Prelude.List
                       Data.Singletons.Prelude.List.NonEmpty
@@ -93,17 +96,21 @@ library
                       Data.Singletons.Prelude.Num
                       Data.Singletons.Prelude.Semigroup
                       Data.Singletons.Prelude.Show
+                      Data.Singletons.Prelude.Traversable
                       Data.Singletons.Prelude.Tuple
                       Data.Singletons.Prelude.Void
                       Data.Promotion.Prelude
                       Data.Promotion.TH
                       Data.Promotion.Prelude.Applicative
                       Data.Promotion.Prelude.Base
                       Data.Promotion.Prelude.Bool
+                      Data.Promotion.Prelude.Const
                       Data.Promotion.Prelude.Either
                       Data.Promotion.Prelude.Eq
+                      Data.Promotion.Prelude.Foldable
                       Data.Promotion.Prelude.Function
                       Data.Promotion.Prelude.Functor
+                      Data.Promotion.Prelude.Identity
                       Data.Promotion.Prelude.IsString
                       Data.Promotion.Prelude.Ord
                       Data.Promotion.Prelude.Enum
@@ -116,6 +123,7 @@ library
                       Data.Promotion.Prelude.Num
                       Data.Promotion.Prelude.Semigroup
                       Data.Promotion.Prelude.Show
+                      Data.Promotion.Prelude.Traversable
                       Data.Promotion.Prelude.Tuple
                       Data.Promotion.Prelude.Void
                       Data.Singletons.TypeError
@@ -132,7 +140,8 @@ library
                       Data.Singletons.Deriving.Show
                       Data.Singletons.Deriving.Util
                       Data.Singletons.Internal
-                      Data.Singletons.Prelude.List.NonEmpty.Internal
+                      Data.Singletons.Prelude.List.Internal
+                      Data.Singletons.Prelude.List.Internal.Disambiguation
                       Data.Singletons.Prelude.Monad.Internal
                       Data.Singletons.Prelude.Semigroup.Internal
                       Data.Singletons.Promote

src/Data/Promotion/Prelude.hs

@@ -53,8 +53,12 @@ module Data.Promotion.Prelude (
   PFunctor(Fmap, type (<$)),
   PApplicative(Pure, type (<*>), type (*>), type (<*)),
   PMonad(type (>>=), type (>>), Return, Fail),
-  -- MapM_,
-  type (=<<),
+  MapM_, Sequence_, type (=<<),
+
+  -- * Promoted 'Foldable' and 'Traversable'
+  PFoldable(Elem, FoldMap, Foldr, Foldl, Foldr1, Foldl1,
+            Maximum, Minimum, Product, Sum),
+  PTraversable(Traverse, SequenceA, MapM, Sequence),
 
   -- ** Miscellaneous functions
   Id, Const, (:.), type ($), type ($!), Flip, AsTypeOf, Until, Seq,
@@ -63,13 +67,9 @@ module Data.Promotion.Prelude (
   Map, type (++), Filter,
   Head, Last, Tail, Init, Null, Length, type (!!),
   Reverse,
-  -- ** Reducing lists (folds)
-  Foldl, Foldl1, Foldr, Foldr1,
   -- *** Special folds
   And, Or, Any, All,
-  Sum, Product,
   Concat, ConcatMap,
-  Maximum, Minimum,
   -- ** Building lists
   -- *** Scans
   Scanl, Scanl1, Scanr, Scanr1,
@@ -80,7 +80,7 @@ module Data.Promotion.Prelude (
   TakeWhile, DropWhile, Span, Break,
 
   -- ** Searching lists
-  Elem, NotElem, Lookup,
+  NotElem, Lookup,
   -- ** Zipping and unzipping lists
   Zip, Zip3, ZipWith, ZipWith3, Unzip, Unzip3,
   -- ** Functions on 'Symbol's
@@ -148,8 +148,26 @@ module Data.Promotion.Prelude (
   type (>>=@#@$), type (>>=@#@$$), type (>>=@#@$$$),
   type (>>@#@$),  type (>>@#@$$),  type (>>@#@$$$),
   ReturnSym0, ReturnSym1, FailSym0, FailSym1,
+  MapM_Sym0, MapM_Sym1, MapM_Sym2,
+  Sequence_Sym0, Sequence_Sym1,
   type (=<<@#@$), type (=<<@#@$$), type (=<<@#@$$$),
 
+  ElemSym0, ElemSym1, ElemSym2,
+  FoldMapSym0, FoldMapSym1, FoldMapSym2,
+  FoldrSym0, FoldrSym1, FoldrSym2, FoldrSym3,
+  FoldlSym0, FoldlSym1, FoldlSym2, FoldlSym3,
+  Foldr1Sym0, Foldr1Sym1, Foldr1Sym2,
+  Foldl1Sym0, Foldl1Sym1, Foldl1Sym2,
+  MaximumSym0, MaximumSym1,
+  MinimumSym0, MinimumSym1,
+  SumSym0, SumSym1,
+  ProductSym0, ProductSym1,
+
+  TraverseSym0, TraverseSym1, TraverseSym2,
+  SequenceASym0, SequenceASym1,
+  MapMSym0, MapMSym1, MapMSym2,
+  SequenceSym0, SequenceSym1,
+
   IdSym0, IdSym1, ConstSym0, ConstSym1, ConstSym2,
   type (.@#@$), type (.@#@$$), type (.@#@$$$),
   type ($@#@$),  type ($@#@$$),  type ($@#@$$$),
@@ -162,11 +180,6 @@ module Data.Promotion.Prelude (
   type (++@#@$$), type (++@#@$), HeadSym0, HeadSym1, LastSym0, LastSym1,
   TailSym0, TailSym1, InitSym0, InitSym1, NullSym0, NullSym1,
 
-  FoldlSym0, FoldlSym1, FoldlSym2, FoldlSym3,
-  Foldl1Sym0, Foldl1Sym1, Foldl1Sym2,
-  FoldrSym0, FoldrSym1, FoldrSym2, FoldrSym3,
-  Foldr1Sym0, Foldr1Sym1, Foldr1Sym2,
-
   ConcatSym0, ConcatSym1,
   ConcatMapSym0, ConcatMapSym1, ConcatMapSym2,
   MaximumBySym0, MaximumBySym1, MaximumBySym2,
@@ -180,7 +193,6 @@ module Data.Promotion.Prelude (
   ScanrSym0, ScanrSym1, ScanrSym2, ScanrSym3,
   Scanr1Sym0, Scanr1Sym1, Scanr1Sym2,
 
-  ElemSym0, ElemSym1, ElemSym2,
   NotElemSym0, NotElemSym1, NotElemSym2,
 
   ZipSym0, ZipSym1, ZipSym2,
@@ -193,8 +205,6 @@ module Data.Promotion.Prelude (
 
   UntilSym0, UntilSym1, UntilSym2, UntilSym3,
   LengthSym0, LengthSym1,
-  SumSym0, SumSym1,
-  ProductSym0, ProductSym1,
   ReplicateSym0, ReplicateSym1, ReplicateSym2,
   TakeSym0, TakeSym1, TakeSym2,
   DropSym0, DropSym1, DropSym2,
@@ -210,8 +220,10 @@ module Data.Promotion.Prelude (
 
 import Data.Promotion.Prelude.Applicative
 import Data.Promotion.Prelude.Base
+  hiding (Foldr, FoldrSym0, FoldrSym1, FoldrSym2, FoldrSym3)
 import Data.Promotion.Prelude.Bool
 import Data.Promotion.Prelude.Either
+import Data.Promotion.Prelude.Foldable
 import Data.Promotion.Prelude.Functor
 import Data.Promotion.Prelude.List
 import Data.Promotion.Prelude.Maybe
@@ -228,4 +240,5 @@ import Data.Promotion.Prelude.Num
 import Data.Promotion.Prelude.Semigroup
        ( PSemigroup(..), type (<>@#@$), type (<>@#@$$), type (<>@#@$$$) )
 import Data.Promotion.Prelude.Show
+import Data.Promotion.Prelude.Traversable
 import Data.Singletons.TypeLits

src/Data/Promotion/Prelude/Const.hs

@@ -0,0 +1,20 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Data.Promotion.Prelude.Const
+-- Copyright   :  (C) 2018 Ryan Scott
+-- License     :  BSD-style (see LICENSE)
+-- Maintainer  :  Richard Eisenberg ([email protected])
+-- Stability   :  experimental
+-- Portability :  non-portable
+--
+-- Exports defunctionalization symbosl for the 'Const' data type.
+--
+-----------------------------------------------------------------------------
+
+module Data.Promotion.Prelude.Const (
+  -- * Defunctionalization symbols
+  ConstSym0, ConstSym1,
+  GetConstSym0, GetConstSym1
+  ) where
+
+import Data.Singletons.Prelude.Const

src/Data/Promotion/Prelude/Foldable.hs

@@ -0,0 +1,67 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Data.Promotion.Prelude.Foldable
+-- Copyright   :  (C) 2018 Ryan Scott
+-- License     :  BSD-style (see LICENSE)
+-- Maintainer  :  Ryan Scott
+-- Stability   :  experimental
+-- Portability :  non-portable
+--
+-- Defines the promoted version of the 'Foldable' type class.
+--
+----------------------------------------------------------------------------
+
+module Data.Promotion.Prelude.Foldable (
+  PFoldable(..),
+
+  FoldrM, FoldlM,
+  Traverse_, For_, SequenceA_, Asum,
+  MapM_, ForM_, Sequence_, Msum,
+  Concat, ConcatMap, And, Or, Any, All, MaximumBy, MinimumBy,
+  NotElem, Find,
+
+  -- * Defunctionalization symbols
+  FoldSym0, FoldSym1,
+  FoldMapSym0, FoldMapSym1, FoldMapSym2,
+  FoldrSym0, FoldrSym1, FoldrSym2, FoldrSym3,
+  Foldr'Sym0, Foldr'Sym1, Foldr'Sym2, Foldr'Sym3,
+  FoldlSym0, FoldlSym1, FoldlSym2, FoldlSym3,
+  Foldl'Sym0, Foldl'Sym1, Foldl'Sym2, Foldl'Sym3,
+  Foldr1Sym0, Foldr1Sym1, Foldr1Sym2,
+  Foldl1Sym0, Foldl1Sym1, Foldl1Sym2,
+  ToListSym0, ToListSym1,
+  NullSym0, NullSym1,
+  LengthSym0, LengthSym1,
+  ElemSym0, ElemSym1, ElemSym2,
+  MaximumSym0, MaximumSym1,
+  MinimumSym0, MinimumSym1,
+  SumSym0, SumSym1,
+  ProductSym0, ProductSym1,
+
+  FoldrMSym0, FoldrMSym1, FoldrMSym2, FoldrMSym3,
+  FoldlMSym0, FoldlMSym1, FoldlMSym2, FoldlMSym3,
+
+  Traverse_Sym0, Traverse_Sym1, Traverse_Sym2,
+  For_Sym0, For_Sym1, For_Sym2,
+  SequenceA_Sym0, SequenceA_Sym1,
+  AsumSym0, AsumSym1,
+
+  MapM_Sym0, MapM_Sym1, MapM_Sym2,
+  ForM_Sym0, ForM_Sym1, ForM_Sym2,
+  Sequence_Sym0, Sequence_Sym1,
+  MsumSym0, MsumSym1,
+
+  ConcatSym0, ConcatSym1,
+  ConcatMapSym0, ConcatMapSym1, ConcatMapSym2,
+  AndSym0, AndSym1,
+  OrSym0, OrSym1,
+  AnySym0, AnySym1, AnySym2,
+  AllSym0, AllSym1, AllSym2,
+  MaximumBySym0, MaximumBySym1, MaximumBySym2,
+  MinimumBySym0, MinimumBySym1, MinimumBySym2,
+
+  NotElemSym0, NotElemSym1, NotElemSym2,
+  FindSym0, FindSym1, FindSym2
+  ) where
+
+import Data.Singletons.Prelude.Foldable

src/Data/Promotion/Prelude/Identity.hs

@@ -0,0 +1,20 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Data.Promotion.Prelude.Identity
+-- Copyright   :  (C) 2018 Ryan Scott
+-- License     :  BSD-style (see LICENSE)
+-- Maintainer  :  Richard Eisenberg ([email protected])
+-- Stability   :  experimental
+-- Portability :  non-portable
+--
+-- Exports the defunctionalization symbols for the 'Identity' data type.
+--
+-----------------------------------------------------------------------------
+
+module Data.Promotion.Prelude.Identity (
+  -- * Defunctionalization symbols
+  IdentitySym0, IdentitySym1,
+  RunIdentitySym0, RunIdentitySym1
+  ) where
+
+import Data.Singletons.Prelude.Identity

src/Data/Promotion/Prelude/List.hs

@@ -230,11 +230,10 @@ module Data.Promotion.Prelude.List (
 
   ) where
 
-import Data.Singletons.Prelude.Base
 import Data.Singletons.Prelude.Eq
 import Data.Singletons.Prelude.List
 import Data.Singletons.Prelude.Maybe
-import Data.Singletons.TH
+import Data.Singletons.TH (promoteOnly)
 
 $(promoteOnly [d|
 

src/Data/Promotion/Prelude/Traversable.hs

@@ -0,0 +1,32 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Data.Promotion.Prelude.Traversable
+-- Copyright   :  (C) 2018 Ryan Scott
+-- License     :  BSD-style (see LICENSE)
+-- Maintainer  :  Ryan Scott
+-- Stability   :  experimental
+-- Portability :  non-portable
+--
+-- Defines the promoted version of the 'Traversable' type class.
+--
+----------------------------------------------------------------------------
+
+module Data.Promotion.Prelude.Traversable (
+  PTraversable(..),
+  For, ForM, MapAccumL, MapAccumR, FmapDefault, FoldMapDefault,
+
+  -- * Defunctionalization symbols
+  TraverseSym0, TraverseSym1, TraverseSym2,
+  SequenceASym0, SequenceASym1,
+  MapMSym0, MapMSym1, MapMSym2,
+  SequenceSym0, SequenceSym1,
+
+  ForSym0, ForSym1, ForSym2,
+  ForMSym0, ForMSym1, ForMSym2,
+  MapAccumLSym0, MapAccumLSym1, MapAccumLSym2, MapAccumLSym3,
+  MapAccumRSym0, MapAccumRSym1, MapAccumRSym2, MapAccumRSym3,
+  FmapDefaultSym0, FmapDefaultSym1, FmapDefaultSym2,
+  FoldMapDefaultSym0, FoldMapDefaultSym1, FoldMapDefaultSym2
+  ) where
+
+import Data.Singletons.Prelude.Traversable