[Git][ghc/ghc][master] Explicit methods for Alternative Compose

[Marge Bot (@marge-bot)]

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC


Commits:
b4f84e4b by James Henri Haydon at 2023-11-16T20:52:53-05:00
Explicit methods for Alternative Compose

Explicitly define some and many in Alternative instance for
Data.Functor.Compose

Implementation of https://github.com/haskell/core-libraries-committee/issues/181

- - - - -


2 changed files:

- libraries/base/changelog.md
- libraries/base/src/Data/Functor/Compose.hs


Changes:

=====================================
libraries/base/changelog.md
=====================================
@@ -11,6 +11,7 @@
   * Export List from Data.List ([CLC proposal #182](https://github.com/haskell/core-libraries-committee/issues/182)).
   * Deprecate `Data.List.NonEmpty.unzip` ([CLC proposal #86](https://github.com/haskell/core-libraries-committee/issues/86))
   * Fix exponent overflow/underflow bugs in the `Read` instances for `Float` and `Double` ([CLC proposal #192](https://github.com/haskell/core-libraries-committee/issues/192))
+  * Implement `many` and `some` methods of `instance Alternative (Compose f g)` explicitly. ([CLC proposal #181](https://github.com/haskell/core-libraries-committee/issues/181))
 
   * The functions `GHC.Exts.dataToTag#` and `GHC.Base.getTag` have had
     their types changed to the following:


=====================================
libraries/base/src/Data/Functor/Compose.hs
=====================================
@@ -147,6 +147,10 @@ instance (Alternative f, Applicative g) => Alternative (Compose f g) where
     empty = Compose empty
     (<|>) = coerce ((<|>) :: f (g a) -> f (g a) -> f (g a))
       :: forall a . Compose f g a -> Compose f g a -> Compose f g a
+    some = coerce (fmap sequenceA . some :: f (g a) -> f (g [a]))
+      :: forall a . Compose f g a -> Compose f g [a]
+    many = coerce (fmap sequenceA . many :: f (g a) -> f (g [a]))
+      :: forall a . Compose f g a -> Compose f g [a]
 
 -- | The deduction (via generativity) that if @g x :~: g y@ then @x :~: y at .
 --



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b4f84e4bfac3648864d9482b7585a01d44b5eb58

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b4f84e4bfac3648864d9482b7585a01d44b5eb58
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