diff options
| -rw-r--r-- | libraries/base/Control/Applicative.hs | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/libraries/base/Control/Applicative.hs b/libraries/base/Control/Applicative.hs index 78e2b4b145..dbfa27268a 100644 --- a/libraries/base/Control/Applicative.hs +++ b/libraries/base/Control/Applicative.hs @@ -230,6 +230,11 @@ newtype Const a b = Const { getConst :: a } instance Functor (Const m) where fmap _ (Const v) = Const v +-- Added in base-4.7.0.0 +instance Monoid a => Monoid (Const a b) where + mempty = Const mempty + mappend (Const a) (Const b) = Const (mappend a b) + instance Monoid m => Applicative (Const m) where pure _ = Const mempty Const f <*> Const v = Const (f `mappend` v) |