Refactor functors and related packages

CHANGELOG.md

@@ -6,6 +6,8 @@ Notable changes to this project are documented in this file. The format is based
 
 Breaking changes:
   - Added support for PureScript 0.14 and dropped support for all previous versions (#16)
+  - `Clown`, `Flip`, `Joker`, and `Product` have been moved to the `Data.Functors` module in the `purescript-functors` package, so that the same types can also be used as profunctors; `Product` was renamed to `Product2` (#22)
+  - `Wrap` was deleted; it is expected that any instances of `Bifunctor` will be accompanied by a corresponding instance of `Functor` (#22)
 
 New features:
 
@@ -14,6 +16,7 @@ Bugfixes:
 Other improvements:
   - Migrated CI to GitHub Actions and updated installation instructions to use Spago (#18)
   - Added a CHANGELOG.md file and pull request template (#19, #20)
+  - This package now depends on the `purescript-const`, `purescript-either`, and `purescript-tuples` packages, and contains instances previously in those packages (#22)
 
 ## [v4.0.0](https://github.com/purescript/purescript-bifunctors/releases/tag/v4.0.0) - 2018-05-23
 

bower.json

@@ -17,7 +17,10 @@
     "package.json"
   ],
   "dependencies": {
+    "purescript-const": "master",
+    "purescript-either": "master",
+    "purescript-newtype": "master",
     "purescript-prelude": "master",
-    "purescript-newtype": "master"
+    "purescript-tuples": "master"
   }
 }

src/Control/Biapplicative.purs

@@ -1,8 +1,12 @@
 module Control.Biapplicative where
 
 import Control.Biapply (class Biapply)
+import Data.Tuple (Tuple(..))
 
 -- | `Biapplicative` captures type constructors of two arguments which support lifting of
 -- | functions of zero or more arguments, in the sense of `Applicative`.
 class Biapply w <= Biapplicative w where
   bipure :: forall a b. a -> b -> w a b
+
+instance biapplicativeTuple :: Biapplicative Tuple where
+  bipure = Tuple

src/Control/Biapply.purs

@@ -3,6 +3,7 @@ module Control.Biapply where
 import Data.Function (const, identity)
 
 import Data.Bifunctor (class Bifunctor, bimap)
+import Data.Tuple (Tuple(..))
 
 -- | A convenience operator which can be used to apply the result of `bipure` in
 -- | the style of `Applicative`:
@@ -53,3 +54,6 @@ bilift3
   -> w c g
   -> w d h
 bilift3 f g a b c = bimap f g <<$>> a <<*>> b <<*>> c
+
+instance biapplyTuple :: Biapply Tuple where
+  biapply (Tuple f g) (Tuple a b) = Tuple (f a) (g b)

src/Data/Bifunctor.purs

@@ -1,6 +1,9 @@
 module Data.Bifunctor where
 
 import Control.Category (identity)
+import Data.Const (Const(..))
+import Data.Either (Either(..))
+import Data.Tuple (Tuple(..))
 
 -- | A `Bifunctor` is a `Functor` from the pair category `(Type, Type)` to `Type`.
 -- |
@@ -25,3 +28,13 @@ lmap f = bimap f identity
 -- | Map a function over the second type arguments of a `Bifunctor`.
 rmap :: forall f a b c. Bifunctor f => (b -> c) -> f a b -> f a c
 rmap = bimap identity
+
+instance bifunctorEither :: Bifunctor Either where
+  bimap f _ (Left l) = Left (f l)
+  bimap _ g (Right r) = Right (g r)
+
+instance bifunctorTuple :: Bifunctor Tuple where
+  bimap f g (Tuple x y) = Tuple (f x) (g y)
+
+instance bifunctorConst :: Bifunctor Const where
+  bimap f _ (Const a) = Const (f a)