Merge pull request #39 from owickstrom/master

Add StateT with Eff example

Author: garyb

Gruntfile.js

@@ -76,6 +76,10 @@ module.exports = function(grunt) {
         src: ["examples/State.purs", "<%=libFiles%>"],
         dest: "tmp/State.js"
       },
+      exampleStateEff: {
+        src: ["examples/StateEff.purs", "<%=libFiles%>"],
+        dest: "tmp/StateEff.js"
+      },
       exampleWriter: {
         src: ["examples/Writer.purs", "<%=libFiles%>"],
         dest: "tmp/Writer.js"
@@ -93,6 +97,9 @@ module.exports = function(grunt) {
       exampleState: {
         src: "tmp/State.js"
       },
+      exampleStateEff: {
+        src: "tmp/StateEff.js"
+      },
       exampleWriter: {
         src: "tmp/Writer.js"
       },
@@ -109,6 +116,7 @@ module.exports = function(grunt) {
 
   grunt.registerTask("exampleReader", ["psc:exampleReader", "execute:exampleReader"]);
   grunt.registerTask("exampleState", ["psc:exampleState", "execute:exampleState"]);
+  grunt.registerTask("exampleStateEff", ["psc:exampleStateEff", "execute:exampleStateEff"]);
   grunt.registerTask("exampleWriter", ["psc:exampleWriter", "execute:exampleWriter"]);
   grunt.registerTask("exampleCont", ["psc:exampleCont", "execute:exampleCont"]);
   grunt.registerTask("examples", ["psc", "execute"]);

examples/StateEff.purs

@@ -0,0 +1,39 @@
+module Main where
+
+import Control.Monad.State
+import Control.Monad.State.Class
+import Control.Monad.State.Trans
+import Control.Monad.Eff
+import Control.Monad.Trans
+import Data.Tuple
+import Debug.Trace
+
+type Stack r t = StateT [Number] (Eff r) t
+
+pop :: forall r. Stack (trace :: Trace | r) Number
+pop = do
+  (x:xs) <- get
+  lift $ trace $ "Popping " ++ show x
+  put xs
+  return x
+
+push :: forall r. Number -> Stack (trace :: Trace | r) Unit
+push x = do
+  lift $ trace $ "Pushing " ++ show x
+  modify $ (:) x
+  return unit
+
+testState :: forall r. Stack (trace :: Trace | r) Number
+testState = do
+  push 1
+  push 2
+  push 3
+  pop
+  pop
+
+main = do
+  result <- runStateT testState []
+  case result of
+    Tuple value state -> do
+      print $ "state: " ++ (show state)
+      print $ "value: " ++ (show value)