Merge pull request #4 from bruderj15/main

Publish v0.1.2

CHANGELOG.md

@@ -6,6 +6,12 @@ file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [PVP versioning](https://pvp.haskell.org/).
 
+## v0.1.2 _(2024-11-29)_
+
+### Added
+- Added type aliases `SomesF` and `SomeF` for existentials with fixed containers
+- Added `mapSome` with infix `(<~$>)` and `traverseSome` with infix `(<~*>)`
+
 ## v0.1.1 _(2024-11-29)_
 
 ### Added

README.md

@@ -7,19 +7,25 @@ It allows you to enforce multiple constraints on polymorphic types and container
 
 ## Core
 
-- **Existential Types**: `Somes` and `Somes1` provide existential wrappers for types with multiple constraints.
-- **Convenient Aliases**: Simplified types `Some` and `Some1` for scenarios where just one constraint is needed.
-
+- **Existential types**: `Somes` and `Somes1` provide existential wrappers for types with multiple constraints.
+- **Convenient aliases**: Simplified types `Some` and `Some1` for scenarios where just one constraint is needed.
+- **More convenient aliases**: Simplified types `SomeF` and `SomesF` for scenarios where the container of a `Somes1` is known.
+- **Natural transformations with constraints**
+    - `mapSome :: (forall a. AllC csa a => f a -> g a) -> SomesF f csa -> SomesF g csa`
+    - `traverseSome :: Functor m => (forall a. AllC csa a => f a -> m (g a)) -> SomesF f csa -> m (SomesF g csa)`
 ## Usage
 
 ```haskell
 import Data.Some.Constraint
 
 someShowableOrd :: Somes '[Show, Ord]
-someShowableOrd = Some (mempty :: [Double])
+someShowableOrd = Some [1, 2, 3 :: Int]
 
 someNumFunctor :: Some1 Functor Num
-someNumFunctor = Some1 $ [1, 2, 3 :: Int]
+someNumFunctor = Some1 [1, 2, 3 :: Int]
+
+someListShowable :: SomeF [] Show
+someListShowable = Some1 [1, 2, 3 :: Int]
 ```
 
 ## Contact information

constrained-some.cabal

@@ -1,6 +1,6 @@
 cabal-version:      3.0
 name:               constrained-some
-version:            0.1.1
+version:            0.1.2
 synopsis:           Existential type that can be constrained
 description:        This library provides utilities for working with existential types and type-level constraints.
   It allows you to enforce multiple constraints on polymorphic types and containers complementing the package some.

src/Data/Some/Constraint.hs

@@ -9,8 +9,27 @@
 {-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE QuantifiedConstraints #-}
 
-module Data.Some.Constraint where
+module Data.Some.Constraint
+(
+  -- * Combining constraints
+  AllC
+
+  -- * Existentials
+  -- ** Flat existentials
+  , Somes(..), Some
+
+  -- ** Containerized existentials
+  -- *** Constrained containers
+  , Somes1(..), Some1
+
+  -- *** Fixed containers
+  , SomesF, SomeF
+  , mapSome, (<~$>)
+  , traverseSome, (<~*>)
+) where
 
 import Data.Kind
 
@@ -34,6 +53,12 @@ data Somes cs where
     (a :: Type).
     AllC cs a => a -> Somes cs
 
+instance {-# OVERLAPPING #-} Show (Somes (Show ': cs)) where
+  showsPrec d (Some x) = showParen (d > 10) $ showString "Some " . showsPrec 11 x
+
+instance {-# OVERLAPPABLE #-} Show (Somes cs) => Show (Somes (c ': cs)) where
+  showsPrec d (Some x) = showsPrec d (Some @cs x)
+
 -- | Alias for 'Somes' with just one 'Constraint'.
 type Some c = Somes '[c]
 
@@ -57,8 +82,32 @@ data Somes1 csf csa where
 -- | Alias for 'Somes1' with just one 'Constraint'.
 type Some1 cf ca = Somes1 '[cf] '[ca]
 
-instance {-# OVERLAPPING #-} Show (Somes (Show ': cs)) where
-  showsPrec d (Some x) = showParen (d > 10) $ showString "Some " . showsPrec 11 x
+-- | Alias for 'Somes1' with a container @f@ and multiple 'Constraint's @csa@ for its elements.
+type SomesF f csa = Somes1 '[(~) f] csa
 
-instance {-# OVERLAPPABLE #-} Show (Somes cs) => Show (Somes (c ': cs)) where
-  showsPrec d (Some x) = showsPrec d (Some @cs x)
+-- | Alias for 'SomeF' with just one 'Constraint' for its elements.
+type SomeF f c = SomesF f '[c]
+
+-- | Natural transformation of one container to another.
+mapSome :: (forall a. AllC csa a => f a -> g a) -> SomesF f csa -> SomesF g csa
+mapSome f (Some1 x) = Some1 (f x)
+
+infixl 4 <~$>
+-- | Infix version of 'mapSome'.
+(<~$>) :: (forall a. AllC csa a => f a -> g a) -> SomesF f csa -> SomesF g csa
+(<~$>) = mapSome
+
+-- | Natural transformation of one container to another - with side effects in @m@.
+traverseSome :: Functor m => (forall a. AllC csa a => f a -> m (g a)) -> SomesF f csa -> m (SomesF g csa)
+traverseSome f (Some1 x) = Some1 <$> f x
+
+infixl 4 <~*>
+-- | Infix version of 'traverseSome'.
+(<~*>) :: Functor m => (forall a. AllC csa a => f a -> m (g a)) -> SomesF f csa -> m (SomesF g csa)
+(<~*>) = traverseSome
+
+instance {-# OVERLAPPING #-} (forall a. Show a => Show (f a)) => Show (SomesF f (Show ': cs)) where
+  showsPrec d (Some1 x) = showParen (d > 10) $ showString "Some " . showsPrec 11 x
+
+instance {-# OVERLAPPABLE #-} Show (SomesF f cs) => Show (SomesF f (c ': cs)) where
+  showsPrec d (Some1 x) = showsPrec d (Some1 @_ @('[(~) f]) @cs x)