Merge pull request #97 from matthewleon/traversable1-instances

Traversable1 instances matching Foldable1 instances

Author: garyb

src/Data/Semigroup/Traversable.purs

@@ -1,8 +1,11 @@
 module Data.Semigroup.Traversable where
 
 import Prelude
-import Data.Traversable (class Traversable)
+
+import Data.Monoid.Dual (Dual(..))
+import Data.Monoid.Multiplicative (Multiplicative(..))
 import Data.Semigroup.Foldable (class Foldable1)
+import Data.Traversable (class Traversable)
 
 -- | `Traversable1` represents data structures with a minimum of one element that can be _traversed_,
 -- | accumulating results and effects in some `Applicative` functor.
@@ -31,6 +34,14 @@ class (Foldable1 t, Traversable t) <= Traversable1 t where
   traverse1 :: forall a b f. Apply f => (a -> f b) -> t a -> f (t b)
   sequence1 :: forall b f. Apply f => t (f b) -> f (t b)
 
+instance traversableDual :: Traversable1 Dual where
+  traverse1 f (Dual x) = Dual <$> f x
+  sequence1 = sequence1Default
+
+instance traversableMultiplicative :: Traversable1 Multiplicative where
+  traverse1 f (Multiplicative x) = Multiplicative <$> f x
+  sequence1 = sequence1Default
+
 -- | A default implementation of `traverse1` using `sequence1`.
 traverse1Default
   :: forall t a b m