From adbdf4507dbba4ce867bd80ad5d1f3b348f539ea Mon Sep 17 00:00:00 2001
From: "John A. De Goes" <john@degoes.net>
Date: Fri, 17 Oct 2014 18:46:09 -0600
Subject: [PATCH] added Enum instance for Either

---
 Gruntfile.js       | 16 ++++++++++++++--
 README.md          |  2 ++
 bower.json         |  1 +
 package.json       |  3 ++-
 src/Data/Enum.purs | 19 ++++++++++++++++++-
 5 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/Gruntfile.js b/Gruntfile.js
index ed5a3d2..d21644f 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -18,13 +18,25 @@ module.exports = function(grunt) {
             src: "src/**/*.purs",
             dest: "README.md"
         }
+    },
+    jsvalidate: {
+      options:{
+        globals: {},
+        esprimaOptions: {},
+        verbose: false
+      },
+      targetName:{
+        files:{
+          src: ['output/Data.Enum/*.js']
+        }
+      }
     }
-
   });
 
+  grunt.loadNpmTasks('grunt-jsvalidate');
   grunt.loadNpmTasks("grunt-contrib-clean");
   grunt.loadNpmTasks("grunt-purescript");
   
-  grunt.registerTask("make", ["pscMake", "dotPsci", "docgen"]);
+  grunt.registerTask("make", ["pscMake", "dotPsci", "docgen", "jsvalidate"]);
   grunt.registerTask("default", ["make"]);
 };
diff --git a/README.md b/README.md
index 4eb2511..ca6cae5 100644
--- a/README.md
+++ b/README.md
@@ -24,6 +24,8 @@
 
     instance enumChar :: Enum Char
 
+    instance enumEither :: (Enum a, Enum b) => Enum (Either a b)
+
     instance enumMaybe :: (Enum a) => Enum (Maybe a)
 
     instance enumTuple :: (Enum a, Enum b) => Enum (Tuple a b)
diff --git a/bower.json b/bower.json
index 0dfa19f..71925b5 100644
--- a/bower.json
+++ b/bower.json
@@ -20,6 +20,7 @@
   "dependencies": {
     "purescript-maybe":   "~0.2.1",
     "purescript-tuples":  "~0.2.1",
+    "purescript-either":  "~0.1.3",
     "purescript-strings": "~0.3.2"
   }
 }
diff --git a/package.json b/package.json
index fa4a87c..8a6ca09 100644
--- a/package.json
+++ b/package.json
@@ -3,6 +3,7 @@
   "dependencies": {
     "grunt": "~0.4.4",
     "grunt-purescript": "~0.5.1",
-    "grunt-contrib-clean": "~0.5.0"
+    "grunt-contrib-clean": "~0.5.0",
+    "grunt-jsvalidate":     "~0.2.2"
   }
 }
diff --git a/src/Data/Enum.purs b/src/Data/Enum.purs
index 467ed7b..9b31f86 100644
--- a/src/Data/Enum.purs
+++ b/src/Data/Enum.purs
@@ -12,6 +12,7 @@ module Data.Enum
   ) where
 
   import Data.Maybe
+  import Data.Either
   import Data.Tuple
   import Data.Char
   import Data.Maybe.Unsafe
@@ -105,4 +106,20 @@ module Data.Enum
     pred (Tuple a b) = maybe (flip Tuple firstEnum <$> pred a) (Just <<< Tuple a) (pred b)
 
   tupleCardinality :: forall a b. (Enum a, Enum b) => Cardinality a -> Cardinality b -> Cardinality (Tuple a b)
-  tupleCardinality l r = Cardinality $ (runCardinality l) * (runCardinality r)
\ No newline at end of file
+  tupleCardinality l r = Cardinality $ (runCardinality l) * (runCardinality r)
+
+  instance enumEither :: (Enum a, Enum b) => Enum (Either a b) where
+    cardinality = eitherCardinality cardinality cardinality
+
+    firstEnum = Left firstEnum
+
+    lastEnum = Right lastEnum
+
+    succ (Left a) = maybe (Just $ Right firstEnum) (Just <<< Left) (succ a)
+    succ (Right b) = maybe (Nothing) (Just <<< Right) (succ b)
+
+    pred (Left a) = maybe (Nothing) (Just <<< Left) (pred a)
+    pred (Right b) = maybe (Just $ Left lastEnum) (Just <<< Right) (pred b)
+
+  eitherCardinality :: forall a b. (Enum a, Enum b) => Cardinality a -> Cardinality b -> Cardinality (Either a b)
+  eitherCardinality l r = Cardinality $ (runCardinality l) + (runCardinality r)
\ No newline at end of file