Make V Monoid

bower.json

@@ -17,6 +17,7 @@
     "package.json"
   ],
   "dependencies": {
-    "purescript-bifunctors": "^3.0.0"
+    "purescript-bifunctors": "^3.0.0",
+    "purescript-monoid": "^3.0.0"
   }
 }

src/Data/Validation/Semigroup.purs

@@ -13,7 +13,10 @@ module Data.Validation.Semigroup
 
 import Prelude
 
+import Control.Apply (lift2)
+
 import Data.Bifunctor (class Bifunctor)
+import Data.Monoid (class Monoid, mempty)
 
 -- | The `V` functor, used for applicative validation
 -- |
@@ -70,3 +73,9 @@ instance applyV :: (Semigroup err) => Apply (V err) where
 
 instance applicativeV :: (Semigroup err) => Applicative (V err) where
   pure = Valid
+
+instance semigroupV :: (Semigroup err, Semigroup a) => Semigroup (V err a) where
+  append = lift2 append
+
+instance monoidV :: (Semigroup err, Monoid a) => Monoid (V err a) where
+  mempty = pure mempty

src/Data/Validation/Semiring.purs

@@ -14,10 +14,12 @@ module Data.Validation.Semiring
 import Prelude
 
 import Control.Alt (class Alt)
+import Control.Apply (lift2)
 import Control.Plus (class Plus)
 import Control.Alternative (class Alternative)
 
 import Data.Bifunctor (class Bifunctor)
+import Data.Monoid (class Monoid, mempty)
 
 -- | The `V` functor, used for alternative validation
 -- |
@@ -77,6 +79,12 @@ instance applyV :: (Semiring err) => Apply (V err)  where
 instance applicativeV :: (Semiring err) => Applicative (V err) where
   pure = Valid
 
+instance semigroupV :: (Semiring err, Semigroup a) => Semigroup (V err a) where
+  append = lift2 append
+
+instance monoidV :: (Semiring err, Monoid a) => Monoid (V err a) where
+  mempty = pure mempty
+
 instance altV :: (Semiring err) => Alt (V err) where
   alt (Invalid err1) (Invalid err2) = Invalid (err1 + err2)
   alt (Invalid _) a = a