diff --git a/Language/MessagePack/IDL/CodeGen/Cpp.hs b/Language/MessagePack/IDL/CodeGen/Cpp.hs
--- a/Language/MessagePack/IDL/CodeGen/Cpp.hs
+++ b/Language/MessagePack/IDL/CodeGen/Cpp.hs
@@ -46,7 +46,7 @@
         | otherwise =
           [lt|#include <msgpack/rpc/client.h>|]
   
-  LT.writeFile (name ++ "_types.hpp") $ templ configFilePath once "TYPES" [lt|
+  LT.writeFile (name ++ "_types.hpp") $ templ configFilePath ns once "TYPES" [lt|
 #include <vector>
 #include <map>
 #include <string>
@@ -57,14 +57,14 @@
 #{genNameSpace ns $ LT.concat $ map (genTypeDecl name) spec }
 |]
 
-  LT.writeFile (name ++ "_server.hpp") $ templ configFilePath once "SERVER" [lt|
+  LT.writeFile (name ++ "_server.hpp") $ templ configFilePath (snoc ns "server") once "SERVER" [lt|
 #include "#{name}_types.hpp"
 #{serverHeader}
 
 #{genNameSpace (snoc ns "server") $ LT.concat $ map (genServer configPFICommon) spec}
 |]
 
-  LT.writeFile (name ++ "_client.hpp") [lt|
+  LT.writeFile (name ++ "_client.hpp") $ templ configFilePath (snoc ns "client") once "CLIENT" [lt|
 #include "#{name}_types.hpp"
 #{clientHeader}
 
@@ -131,12 +131,12 @@
   where
   genMethodDispatch Function {..} =
     -- TODO: FIX IT!
-    let typs = map (genType . maybe TVoid fldType) $ sortField methodArgs in
+    let typs = map (genRetType . maybe Nothing (Just . fldType)) $ sortField methodArgs in
     let params = map g methodArgs in
     case params of
       [] -> [lt|
       if (method == "#{methodName}") {
-        req.result<#{genType methodRetType} >(static_cast<Impl*>(this)->#{methodName}());
+        req.result<#{genRetType methodRetType} >(static_cast<Impl*>(this)->#{methodName}());
         return;
       }
 |]
@@ -144,7 +144,7 @@
       if (method == "#{methodName}") {
         msgpack::type::tuple<#{LT.intercalate ", " typs} > params;
         req.params().convert(&params);
-        req.result<#{genType methodRetType} >(static_cast<Impl*>(this)->#{methodName}(#{LT.intercalate ", " params}));
+        req.result<#{genRetType methodRetType} >(static_cast<Impl*>(this)->#{methodName}(#{LT.intercalate ", " params}));
         return;
       }
 |]
@@ -164,8 +164,8 @@
 |]
   where
     genSetMethod Function {..} =
-      let typs = map (genType . maybe TVoid fldType) $ sortField methodArgs
-          sign = [lt|#{genType methodRetType}(#{LT.intercalate ", " typs})|]
+      let typs = map (genRetType . maybe Nothing (Just . fldType)) $ sortField methodArgs
+          sign = [lt|#{genRetType methodRetType}(#{LT.intercalate ", " typs})|]
           phs  = LT.concat $ [[lt|, pfi::lang::_#{show ix}|] | ix <- [1 .. length (typs)]]
       in [lt|
     rpc_server::add<#{sign} >("#{methodName}", pfi::lang::bind(&Impl::#{methodName}, static_cast<Impl*>(this)#{phs}));|]
@@ -190,14 +190,14 @@
     let args = LT.intercalate ", " $ map arg methodArgs in
     let vals = LT.concat $ map val methodArgs in
     case methodRetType of
-      TVoid -> [lt|
+      Nothing -> [lt|
     void #{methodName}(#{args}) {
       c_.call("#{methodName}"#{vals});
     }
 |]
-      _ -> [lt|
-    #{genType methodRetType} #{methodName}(#{args}) {
-      return c_.call("#{methodName}"#{vals}).get<#{genType methodRetType} >();
+      Just typ -> [lt|
+    #{genType typ} #{methodName}(#{args}) {
+      return c_.call("#{methodName}"#{vals}).get<#{genType typ} >();
     }
 |]
     where
@@ -217,18 +217,18 @@
 |]
   where
   genMethodCall Function {..} =
-    let typs = map (genType . maybe TVoid fldType) $ sortField methodArgs
-        sign = [lt|#{genType methodRetType}(#{LT.intercalate ", " typs})|]
+    let typs = map (genRetType . maybe Nothing (\f -> Just (fldType f))) $ sortField methodArgs
+        sign = [lt|#{genRetType methodRetType}(#{LT.intercalate ", " typs})|]
         args = LT.intercalate ", " $ map arg methodArgs
         vals = LT.intercalate ", " $ map val methodArgs in
     case methodRetType of
-      TVoid -> [lt|
+      Nothing -> [lt|
     void #{methodName}(#{args}) {
       call<#{sign}>("#{methodName}")(#{vals});
     }
 |]
-      _ -> [lt|
-    #{genType methodRetType} #{methodName}(#{args}) {
+      Just t -> [lt|
+    #{genType t} #{methodName}(#{args}) {
       return call<#{sign}>("#{methodName}")(#{vals});
     }
 |]
@@ -265,21 +265,25 @@
   foldr1 (\t1 t2 -> [lt|std::pair<#{t1}, #{t2} >|]) $ map genType ts
 genType TObject =
   [lt|msgpack::object|]
-genType TVoid =
-  [lt|void|]
 
-templ :: FilePath -> String -> String -> LT.Text -> LT.Text
-templ filepath once name content = [lt|
+genRetType :: Maybe Type -> LT.Text
+genRetType Nothing = [lt|void|]
+genRetType (Just t) = genType t
+
+templ :: FilePath -> [LT.Text] -> String -> String -> LT.Text -> LT.Text
+templ filepath ns once name content = [lt|
 // This file is auto-generated from #{filepath}
 // *** DO NOT EDIT ***
 
-#ifndef #{once}_#{name}_HPP_
-#define #{once}_#{name}_HPP_
+#ifndef #{namespace}_#{once}_#{name}_HPP_
+#define #{namespace}_#{once}_#{name}_HPP_
 
 #{content}
 
-#endif // #{once}_#{name}_HPP_
-|]
+#endif // #{namespace}_#{once}_#{name}_HPP_
+|] where
+   namespace = LT.intercalate "_" $ map LT.toUpper ns
+
 
 genNameSpace :: [LT.Text] -> LT.Text -> LT.Text
 genNameSpace namespace content = f namespace
diff --git a/Language/MessagePack/IDL/CodeGen/Erlang.hs b/Language/MessagePack/IDL/CodeGen/Erlang.hs
new file mode 100644
--- /dev/null
+++ b/Language/MessagePack/IDL/CodeGen/Erlang.hs
@@ -0,0 +1,189 @@
+{-# LANGUAGE QuasiQuotes, RecordWildCards, OverloadedStrings #-}
+
+module Language.MessagePack.IDL.CodeGen.Erlang (
+  Config(..),
+  generate,
+  ) where
+
+import Data.Char
+import Data.List
+import qualified Data.Text as T
+import qualified Data.Text.Lazy as LT
+import qualified Data.Text.Lazy.IO as LT
+import System.FilePath
+import Text.Shakespeare.Text
+
+import Language.MessagePack.IDL.Syntax
+
+data Config
+  = Config
+    { configFilePath :: FilePath
+    }
+  deriving (Show, Eq)
+
+generate:: Config -> Spec -> IO ()
+generate Config {..} spec = do
+  let name = takeBaseName configFilePath
+      once = map toUpper name
+
+      headerFile = name ++ "_types.hrl"
+
+  LT.writeFile (headerFile) $ templ configFilePath once "TYPES" [lt|
+-ifndef(#{once}).
+-define(#{once}, 1).
+
+-type mp_string() :: binary().
+
+#{LT.concat $ map (genTypeDecl name) spec }
+
+-endif.
+|]
+
+  LT.writeFile (name ++ "_server.tmpl.erl") $ templ configFilePath once "SERVER" [lt|
+
+-module(#{name}_server).
+-author('@msgpack-idl').
+
+-include("#{headerFile}").
+
+#{LT.concat $ map genServer spec}
+|]
+
+  LT.writeFile (name ++ "_client.erl") [lt|
+% This file is automatically generated by msgpack-idl.
+-module(#{name}_client).
+-author('@msgpack-idl').
+
+-include("#{headerFile}").
+-export([connect/3, close/1]).
+
+#{LT.concat $ map genClient spec}
+|]
+
+genTypeDecl :: String -> Decl -> LT.Text
+genTypeDecl _ MPMessage {..} =
+  genMsg msgName msgFields False
+
+genTypeDecl _ MPException {..} =
+  genMsg excName excFields True
+
+genTypeDecl _ MPType { .. } =
+  [lt|
+-type #{tyName}() :: #{genType tyType}.
+|]
+
+genTypeDecl _ _ = ""
+
+genMsg name flds isExc =
+  let fields = map f flds
+  in [lt|
+-type #{name}() :: [
+      #{LT.intercalate "\n    | " fields}
+    ]. % #{e}
+|]
+  where
+    e = if isExc then [lt| (exception)|] else ""
+    f Field {..} = [lt|#{genType fldType} %  #{fldName}|]
+
+sortField flds =
+  flip map [0 .. maximum $ [-1] ++ map fldId flds] $ \ix ->
+  find ((==ix). fldId) flds
+
+makeExport i Function {..} =
+  let j = i + length methodArgs in
+  [lt|#{methodName}/#{show j}|]
+makeExport _ _ = ""
+
+
+genServer :: Decl -> LT.Text
+genServer MPService {..} = [lt|
+
+-export([#{LT.intercalate ", " $ map (makeExport 0) serviceMethods}]).
+
+#{LT.concat $ map genSetMethod serviceMethods}
+
+|]
+  where
+    genSetMethod Function {..} =
+      let typs = map (genRetType . maybe Nothing (Just . fldType)) $ sortField methodArgs
+          args = map f methodArgs
+          f Field {..} = [lt|#{capitalize0 fldName}|]
+          capitalize0 str = T.cons (toUpper $ T.head str) (T.tail str)
+
+      in [lt|
+-spec #{methodName}(#{LT.intercalate ", " typs}) -> #{genRetType methodRetType}.
+#{methodName}(#{LT.intercalate ", " args}) ->
+  Reply = <<"ok">>,  % write your code here
+  Reply.
+|]
+    genSetMethod _ = ""
+
+genServer _ = ""
+
+genClient :: Decl -> LT.Text
+genClient MPService {..} = [lt|
+
+-export([#{LT.intercalate ", " $ map (makeExport 1) serviceMethods}]).
+
+-spec connect(inet:ip_address(), inet:port_number(), [proplists:property()]) -> {ok, pid()} | {error, any()}.
+connect(Host,Port,Options)->
+    msgpack_rpc_client:connect(tcp,Host,Port,Options).
+
+-spec close(pid())-> ok.
+close(Pid)->
+    msgpack_rpc_client:close(Pid).
+
+#{LT.concat $ map genMethodCall serviceMethods}
+|]
+  where
+  genMethodCall Function {..} =
+      let typs = map (genRetType . maybe Nothing (Just . fldType)) $ sortField methodArgs
+          args = map f methodArgs
+          f Field {..} = [lt|#{capitalize0 fldName}|]
+          capitalize0 str = T.cons (toUpper $ T.head str) (T.tail str)
+      in [lt|
+-spec #{methodName}(pid(), #{LT.intercalate ", " typs}) -> #{genRetType methodRetType}.
+#{methodName}(Pid, #{LT.intercalate ", " args}) ->
+    msgpack_rpc_client:call(Pid, #{methodName}, [#{LT.intercalate ", " args}]).
+|]
+    where
+      arg Field {..} = [lt|#{genType fldType} #{fldName}|]
+      val Field {..} = [lt|#{fldName}|]
+
+  genMethodCall _ = ""
+
+genClient _ = ""
+
+genType :: Type -> LT.Text
+genType (TInt sign bits) =
+  let base = if sign then "non_neg_integer" else "integer" :: LT.Text in
+  [lt|#{base}()|]
+genType (TFloat _) =
+  [lt|float()|]
+genType TBool =
+  [lt|boolean()|]
+genType TRaw =
+  [lt|binary()|]
+genType TString =
+  [lt|mp_string()|]
+genType (TList typ) =
+  [lt|list(#{genType typ})|]
+genType (TMap typ1 typ2) =
+  [lt|list({#{genType typ1}, #{genType typ2}})|]
+genType (TUserDef className params) =
+  [lt|#{className}()|]
+genType (TTuple ts) =
+  -- TODO: FIX
+  foldr1 (\t1 t2 -> [lt|{#{t1}, #{t2}}|]) $ map genType ts
+genType TObject =
+  [lt|term()|]
+
+genRetType :: Maybe Type -> LT.Text
+genRetType Nothing = [lt|void()|]
+genRetType (Just t) = genType t
+
+templ :: FilePath -> String -> String -> LT.Text -> LT.Text
+templ filepath once name content = [lt|
+% This file is auto-generated from #{filepath}
+
+#{content}|]
diff --git a/Language/MessagePack/IDL/CodeGen/Haskell.hs b/Language/MessagePack/IDL/CodeGen/Haskell.hs
--- a/Language/MessagePack/IDL/CodeGen/Haskell.hs
+++ b/Language/MessagePack/IDL/CodeGen/Haskell.hs
@@ -67,7 +67,7 @@
     monadName = classize (serviceName) `mappend` "T"
     genMethod Function {..} =
       let ts = map (genType . fldType) methodArgs in
-      let typs = ts ++ [ [lt|#{monadName} (#{genType methodRetType})|] ] in
+      let typs = ts ++ [ [lt|#{monadName} (#{genRetType methodRetType})|] ] in
       [lt|
 #{methodize methodName} :: #{LT.intercalate " -> " typs}
 #{methodize methodName} = MP.method "#{methodName}"
@@ -119,9 +119,11 @@
   [lt|#{classize name}|]
 genType (TObject) =
   undefined
-genType (TVoid) =
-  [lt|()|]
 
+genRetType :: Maybe Type -> LT.Text
+genRetType Nothing = "()"
+genRetType (Just t) = genType t
+
 classize :: T.Text -> T.Text
 classize = capital . camelize
 
@@ -198,9 +200,6 @@
 
 genType (TTuple typs) =
   foldl appT (tupleT (length typs)) (map genType typs)
-
-genType TVoid =
-  tupleT 0
 
 capital (c:cs) = toUpper c : cs
 capital cs = cs
diff --git a/Language/MessagePack/IDL/CodeGen/Java.hs b/Language/MessagePack/IDL/CodeGen/Java.hs
--- a/Language/MessagePack/IDL/CodeGen/Java.hs
+++ b/Language/MessagePack/IDL/CodeGen/Java.hs
@@ -11,6 +11,7 @@
 import qualified Data.Text.Lazy as LT
 import qualified Data.Text.Lazy.IO as LT
 import System.FilePath
+import System.Directory
 import Text.Shakespeare.Text
 
 import Language.MessagePack.IDL.Syntax
@@ -25,11 +26,13 @@
 generate :: Config -> Spec -> IO()
 generate config spec = do
   let typeAlias = map genAlias $ filter isMPType spec
+      dirName = joinPath $ map LT.unpack $ LT.split (== '.') $ LT.pack $ configPackage config
 
   genTuple config
+  createDirectoryIfMissing True dirName
   mapM_ (genClient typeAlias config) spec
-  mapM_ (genStruct typeAlias $ configPackage config) spec
-  mapM_ (genException $ configPackage config) spec
+  mapM_ (genStruct typeAlias config) spec
+  mapM_ (genException typeAlias config) spec
 
 {--
   LT.writeFile (name ++ "Server.java") $ templ (configFilePath ++ configPackage ++"/server/")[lt|
@@ -56,21 +59,26 @@
 |]
 genImport _ _ = ""
 
-genStruct :: [(T.Text, Type)] -> FilePath -> Decl -> IO()
-genStruct alias packageName MPMessage {..} = do
+genStruct :: [(T.Text, Type)] -> Config -> Decl -> IO()
+genStruct alias Config{..} MPMessage {..} = do
   let params = if null msgParam then "" else [lt|<#{T.intercalate ", " msgParam}>|]
       resolvedMsgFields = map (resolveFieldAlias alias) msgFields
       hashMapImport | not $ null [() | TMap _ _ <- map fldType resolvedMsgFields] = [lt|import java.util.HashMap;|]
                     | otherwise = ""
       arrayListImport | not $ null [() | TList _ <- map fldType resolvedMsgFields] = [lt|import java.util.ArrayList;|]
                       | otherwise = ""
+      dirName = joinPath $ map LT.unpack $ LT.split (== '.') $ LT.pack configPackage
+      fileName =  dirName ++ "/" ++ (T.unpack $ formatClassNameT msgName) ++ ".java"
 
-  LT.writeFile ( (formatClassName $ T.unpack msgName) ++ ".java") [lt|
-package #{packageName};
+  LT.writeFile fileName $ templ configFilePath [lt|
+package #{configPackage};
 
 #{hashMapImport}
 #{arrayListImport}
+import org.msgpack.MessagePack;
+import org.msgpack.annotation.Message;
 
+@Message
 public class #{formatClassNameT msgName} #{params} {
 
 #{LT.concat $ map genDecl resolvedMsgFields}
@@ -82,15 +90,15 @@
 genStruct _ _ _ = return ()
 
 resolveMethodAlias :: [(T.Text, Type)] -> Method -> Method
-resolveMethodAlias alias Function {..}  = Function methodInherit methodName (resolveTypeAlias alias methodRetType) (map (resolveFieldAlias alias) methodArgs)
+resolveMethodAlias alias Function {..}  = Function methodInherit methodName (resolveRetTypeAlias alias methodRetType) (map (resolveFieldAlias alias) methodArgs)
 resolveMethodAlias _ f = f
 
 resolveFieldAlias :: [(T.Text, Type)] -> Field -> Field
 resolveFieldAlias alias Field {..} = Field fldId (resolveTypeAlias alias fldType) fldName fldDefault
 
 resolveTypeAlias :: [(T.Text, Type)] -> Type -> Type
-resolveTypeAlias alias ty = let fixedAlias = resolveTypeAlias alias in 
-                           case ty of
+resolveTypeAlias alias ty = let fixedAlias = resolveTypeAlias alias in
+                            case ty of
                              TNullable t ->
                                  TNullable $ fixedAlias t
                              TList t ->
@@ -103,8 +111,12 @@
                                  case lookup className alias of 
                                    Just resolvedType -> resolvedType
                                    Nothing -> TUserDef className (map fixedAlias params)
-                             otherwise -> ty
+                             _ -> ty
 
+resolveRetTypeAlias :: [(T.Text, Type)] -> Maybe Type -> Maybe Type
+resolveRetTypeAlias alias Nothing = Nothing
+resolveRetTypeAlias alias (Just t) = Just (resolveTypeAlias alias t)
+
 genInit :: Field -> LT.Text
 genInit Field {..} = case fldDefault of
                       Nothing -> ""
@@ -115,13 +127,16 @@
     [lt|  public #{genType fldType} #{fldName};
 |]
 
-genException :: FilePath -> Decl -> IO()
-genException packageName MPException {..} = do
-  LT.writeFile ( (formatClassName $ T.unpack excName) ++ ".java") [lt|
-package #{packageName};
+genException :: [(T.Text, Type)] -> Config -> Decl -> IO()
+genException alias Config{..} MPException{..} = do
+  LT.writeFile ( (formatClassName $ T.unpack excName) ++ ".java") $ templ configFilePath [lt|
+package #{configPackage};
 
-public class #{formatClassNameT excName} #{params}{
+import org.msgpack.MessagePack;
+import org.msgpack.annotation.Message;
 
+@Message
+public class #{formatClassNameT excName} #{params}{
 #{LT.concat $ map genDecl excFields}
   public #{formatClassNameT excName}() {
   #{LT.concat $ map genInit excFields}
@@ -133,17 +148,19 @@
     super = case excSuper of 
               Just x -> [st|extends #{x}|]
               Nothing -> ""
-genException _ _ = return ()
+genException _ _ _  = return ()
 
 genClient :: [(T.Text, Type)] -> Config -> Decl -> IO()
 genClient alias Config {..} MPService {..} = do 
   let resolvedServiceMethods = map (resolveMethodAlias alias) serviceMethods
-      hashMapImport | not $ null [() | TMap _ _ <- map methodRetType resolvedServiceMethods ] = [lt|import java.util.HashMap;|]
+      hashMapImport | not $ null [() | Just (TMap _ _) <- map methodRetType resolvedServiceMethods ] = [lt|import java.util.HashMap;|]
                     | otherwise = ""
-      arrayListImport | not $ null [() | TList _ <- map methodRetType resolvedServiceMethods] = [lt|import java.util.ArrayList;|]
+      arrayListImport | not $ null [() | Just (TList _) <- map methodRetType resolvedServiceMethods] = [lt|import java.util.ArrayList;|]
                       | otherwise = ""
+      dirName = joinPath $ map LT.unpack $ LT.split (== '.') $ LT.pack configPackage
+      fileName =  dirName ++ "/" ++ (T.unpack className) ++ ".java"
 
-  LT.writeFile (T.unpack className ++ ".java") $ templ configFilePath [lt|
+  LT.writeFile fileName $ templ configFilePath [lt|
 package #{configPackage};
 
 #{hashMapImport}
@@ -173,13 +190,13 @@
         let args = T.intercalate ", " $ map genArgs' methodArgs
             vals = T.intercalate ", " $ pack methodArgs genVal in
         case methodRetType of
-          TVoid -> [lt|
+          Nothing -> [lt|
   public void #{methodName}(#{args}) {
     iface_.#{methodName}(#{vals});
   }
 |]
-          _ -> [lt|
-  public #{genType methodRetType} #{methodName}(#{args}) {
+          Just typ -> [lt|
+  public #{genType typ} #{methodName}(#{args}) {
     return iface_.#{methodName}(#{vals});
   }
 |]
@@ -189,7 +206,7 @@
 
 genSignature :: Method -> LT.Text
 genSignature Function {..} = 
-    [lt|    #{genType methodRetType} #{methodName}(#{args});
+    [lt|    #{genRetType methodRetType} #{methodName}(#{args});
 |]
     where
       args = (T.intercalate ", " $ map genArgs' methodArgs)
@@ -265,9 +282,11 @@
   foldr1 (\t1 t2 -> [lt|Tuple<#{t1}, #{t2} >|]) $ map genWrapperType ts
 genType TObject =
   [lt|org.msgpack.type.Value|]
-genType TVoid =
-  [lt|void|]
 
+genRetType :: Maybe Type -> LT.Text
+genRetType Nothing = [lt|void|]
+genRetType (Just t) = genType t
+
 genTypeWithContext :: Spec -> Type -> LT.Text
 genTypeWithContext spec t = case t of 
                               (TUserDef className params) -> 
@@ -317,8 +336,8 @@
   foldr1 (\t1 t2 -> [lt|Tuple<#{t1}, #{t2} >|]) $ map genWrapperType ts
 genWrapperType TObject =
   [lt|org.msgpack.type.Value|]
-genWrapperType TVoid =
-  [lt|void|]
+genWrapperType (TNullable typ) =
+  genWrapperType typ
 
 templ :: FilePath -> LT.Text -> LT.Text
 templ filepath content = [lt|
diff --git a/Language/MessagePack/IDL/CodeGen/Perl.hs b/Language/MessagePack/IDL/CodeGen/Perl.hs
--- a/Language/MessagePack/IDL/CodeGen/Perl.hs
+++ b/Language/MessagePack/IDL/CodeGen/Perl.hs
@@ -91,50 +91,8 @@
 
 1;
 |]
-  where
-  genMethodCall Function {..} =
-    let args = LT.intercalate ", " $ map arg methodArgs in
-    let vals = LT.concat $ map val methodArgs in
-    [lt|
-    #{genType methodRetType} #{methodName}(#{args}) {
-      return c_.call("#{methodName}"#{vals}).get<#{genType methodRetType} >();
-    }
-|]
-    where
-      arg Field {..} = [lt|#{genType fldType} #{fldName}|]
-      val Field {..} = [lt|, #{fldName}|]
 
-  genMethodCall _ = ""
-
 genClient _ = ""
-
-genType :: Type -> LT.Text
-genType (TInt sign bits) =
-  let base = if sign then "int" else "uint" :: LT.Text in
-  [lt|#{base}#{show bits}_t|]
-genType (TFloat False) =
-  [lt|float|]
-genType (TFloat True) =
-  [lt|double|]
-genType TBool =
-  [lt|bool|]
-genType TRaw =
-  [lt|std::string|]
-genType TString =
-  [lt|std::string|]
-genType (TList typ) =
-  [lt|std::vector<#{genType typ} >|]
-genType (TMap typ1 typ2) =
-  [lt|std::map<#{genType typ1}, #{genType typ2} >|]
-genType (TUserDef className params) =
-  [lt|#{className}|]
-genType (TTuple ts) =
-  -- TODO: FIX
-  foldr1 (\t1 t2 -> [lt|std::pair<#{t1}, #{t2} >|]) $ map genType ts
-genType TObject =
-  [lt|msgpack::object|]
-genType TVoid =
-  [lt|void|]
 
 templ :: FilePath -> String -> String -> LT.Text -> LT.Text
 templ filepath once name content = [lt|
diff --git a/Language/MessagePack/IDL/CodeGen/Php.hs b/Language/MessagePack/IDL/CodeGen/Php.hs
--- a/Language/MessagePack/IDL/CodeGen/Php.hs
+++ b/Language/MessagePack/IDL/CodeGen/Php.hs
@@ -134,15 +134,15 @@
     let args = LT.intercalate ", " $ map arg methodArgs in
     let sortedArgs = LT.intercalate ", " $ map (maybe undefined arg) $ sortField methodArgs in
     case methodRetType of
-      TVoid -> [lt|
+      Nothing -> [lt|
   public function #{methodName}(#{args}) {
     $this->client->call("#{methodName}", array(#{sortedArgs}));
   }
 |]
-      _ -> [lt|
+      Just typ -> [lt|
   public function #{methodName}(#{args}) {
     $ret = $this->client->call("#{methodName}", array(#{sortedArgs}));
-    $type_array = #{genTypeArray methodRetType};
+    $type_array = #{genTypeArray typ};
     return ObjectDecoder::decodeToObject($ret, $type_array);
   }
 |]
diff --git a/Language/MessagePack/IDL/CodeGen/Python.hs b/Language/MessagePack/IDL/CodeGen/Python.hs
--- a/Language/MessagePack/IDL/CodeGen/Python.hs
+++ b/Language/MessagePack/IDL/CodeGen/Python.hs
@@ -6,6 +6,7 @@
   ) where
 
 import Data.List
+import Data.Monoid
 import qualified Data.Text as T
 import qualified Data.Text.Lazy as LT
 import qualified Data.Text.Lazy.IO as LT
@@ -24,7 +25,7 @@
 generate Config {..} spec = do
   createDirectoryIfMissing True (takeBaseName configFilePath);
   setCurrentDirectory (takeBaseName configFilePath);
-  LT.writeFile "__init__.py" $ [lt|
+  LT.writeFile "__init__.py" $ templ configFilePath [lt|
 |]
   LT.writeFile "types.py" $ templ configFilePath [lt|
 import sys
@@ -33,14 +34,14 @@
 #{LT.concat $ map (genTypeDecl "") spec }
 |]
 
-  LT.writeFile "server.tmpl.py" $ [lt|
+  LT.writeFile "server.tmpl.py" $ templ configFilePath [lt|
 import msgpackrpc
 from types import *
 # write your server here and change file name to server.py
 
 |]
 
-  LT.writeFile "client.py" [lt|
+  LT.writeFile "client.py" $ templ configFilePath [lt|
 import msgpackrpc
 from types import *
 
@@ -66,8 +67,7 @@
 
 genMsg :: ToText a => a -> [Field] -> Bool -> LT.Text
 genMsg name flds isExc =
-  let
-      fs = map (maybe undefined fldName) $ sortField flds
+  let fs = zipWith (\ix -> maybe ("_UNUSED" `mappend` T.pack (show ix)) fldName) [0 .. ] (sortField flds)
   in [lt|
 class #{name}#{e}:
   def __init__(self, #{LT.intercalate ", " $ map g fs}):
@@ -108,15 +108,15 @@
 |]
   where
   genMethodCall Function {..} =
-    let arg_list = map (maybe undefined fldName) $ sortField methodArgs
+    let arg_list = zipWith (\ix -> maybe ("_UNUSED" `mappend` T.pack (show ix)) fldName) [0 .. ] $ sortField methodArgs
         args = LT.concat $ map (\x -> [lt|, #{x}|]) arg_list
     in
     case methodRetType of
-      TVoid -> [lt|
+      Nothing -> [lt|
   def #{methodName} (self#{args}):
     self.client.call('#{methodName}'#{args})
 |]
-      ts -> [lt|
+      Just ts -> [lt|
   def #{methodName} (self#{args}):
     retval = self.client.call('#{methodName}'#{args})
     return #{fromMsgpack ts "retval"}
@@ -155,15 +155,13 @@
             
 fromMsgpack (TTuple ts) name =
             let elems = map (f name) (zip [0..] ts) in
-            [lt| (#{LT.concat elems}) |]
+            [lt| (#{LT.intercalate ", " elems}) |]
             where
               f :: T.Text -> (Integer, Type) -> LT.Text
-              f n (i, (TUserDef className _ )) = [lt|#{className}.from_msgpack(#{n}[#{show i}], |]
-              f n (i, _) = [lt|#{n}[#{show i}], |]
+              f n (i, (TUserDef className _ )) = [lt|#{className}.from_msgpack(#{n}[#{show i}]) |]
+              f n (i, _) = [lt|#{n}[#{show i}]|]
 
 fromMsgpack TObject name = [lt|#{name}|]
-fromMsgpack TVoid _ = ""
-
 
 templ :: FilePath -> LT.Text -> LT.Text
 templ filepath content = [lt|
diff --git a/Language/MessagePack/IDL/CodeGen/Ruby.hs b/Language/MessagePack/IDL/CodeGen/Ruby.hs
--- a/Language/MessagePack/IDL/CodeGen/Ruby.hs
+++ b/Language/MessagePack/IDL/CodeGen/Ruby.hs
@@ -31,14 +31,16 @@
   let
         mods = LT.splitOn "::" $ LT.pack configModule
         
-  LT.writeFile "types.rb" $ [lt|
+  LT.writeFile "types.rb" $ templ configFilePath [lt|
+require 'rubygems'
 require 'msgpack/rpc'
 #{genModule mods $ LT.concat $ map (genTypeDecl "") spec }
 |]
   
   LT.writeFile ("client.rb") $ templ configFilePath [lt|
+require 'rubygems'
 require 'msgpack/rpc'
-require './types'
+require File.join(File.dirname(__FILE__), 'types')
 
 #{genModule (snoc mods "Client") $ LT.concat $ map genClient spec}|]
 
@@ -136,14 +138,13 @@
 
 fromTuple (TTuple ts) name =
   let elems = map (f name) (zip [0..] ts) in
-  [lt| [#{LT.concat elems}] |]
+  [lt| [#{LT.intercalate ", " elems}] |]
     where
       f :: T.Text -> (Integer, Type) -> LT.Text
-      f n (i, (TUserDef className _ )) = [lt|#{capitalizeT className}.from_tuple(#{n}[#{show i}], |]
-      f n (i, _) = [lt|#{n}[#{show i}], |]
+      f n (i, (TUserDef className _ )) = [lt|#{capitalizeT className}.from_tuple(#{n}[#{show i}]) |]
+      f n (i, _) = [lt|#{n}[#{show i}] |]
 
 fromTuple (TObject) name = [lt|#{name}|]
-fromTuple TVoid _ = ""
 
 capitalizeT :: T.Text -> T.Text
 capitalizeT a = T.cons (toUpper $ T.head a) (T.tail a)
@@ -260,8 +261,8 @@
 #{capitalizeT t}.from_tuple(#{unpacked})|]
 genConvertingType _ _ _ = ""
 
-genConvertingType' :: LT.Text -> LT.Text -> Type -> LT.Text
-genConvertingType' unpacked v (TUserDef t p) = [lt|
+genConvertingType' :: LT.Text -> LT.Text -> Maybe Type -> LT.Text
+genConvertingType' unpacked v (Just (TUserDef t p)) = [lt|
 #{genConvertingType unpacked v (TUserDef t p)}
 |]
 genConvertingType' unpacked _ _ = [lt|#{unpacked}|]
diff --git a/Language/MessagePack/IDL/Syntax.hs b/Language/MessagePack/IDL/Syntax.hs
--- a/Language/MessagePack/IDL/Syntax.hs
+++ b/Language/MessagePack/IDL/Syntax.hs
@@ -46,7 +46,7 @@
   = Function
     { methodInherit :: Bool
     , methodName :: T.Text
-    , methodRetType :: Type
+    , methodRetType :: Maybe Type
     , methodArgs :: [Field]
     }
   | InheritName T.Text
@@ -65,7 +65,6 @@
   | TTuple [Type]
   | TUserDef T.Text [Type]
   | TObject
-  | TVoid
   deriving (Eq, Show, Data, Typeable)
 
 data Literal
diff --git a/exec/main.hs b/exec/main.hs
--- a/exec/main.hs
+++ b/exec/main.hs
@@ -14,6 +14,7 @@
 import qualified Language.MessagePack.IDL.CodeGen.Php as Php
 import qualified Language.MessagePack.IDL.CodeGen.Python as Python
 import qualified Language.MessagePack.IDL.CodeGen.Perl as Perl
+import qualified Language.MessagePack.IDL.CodeGen.Erlang as Erlang
 
 import Paths_msgpack_idl
 
@@ -49,6 +50,9 @@
     { output_dir :: FilePath
     , namespace :: String
     , filepath :: FilePath }
+  | Erlang
+    { output_dir :: FilePath
+    , filepath :: FilePath }
   deriving (Show, Eq, Data, Typeable)
 
 main :: IO ()
@@ -88,6 +92,10 @@
             , namespace = "msgpack"
             , filepath = def &= argPos 0
             }
+          , Erlang
+            { output_dir = def
+            , filepath = def &= argPos 0
+            }
           ]
     &= help "MessagePack RPC IDL Compiler"
     &= summary ("mpidl " ++ showVersion version)
@@ -124,3 +132,7 @@
  
           Ruby {..} -> do
             Ruby.generate (Ruby.Config filepath modules) spec
+          
+          Erlang {..} -> do
+            Erlang.generate (Erlang.Config filepath) spec
+
diff --git a/mpidl.peggy b/mpidl.peggy
--- a/mpidl.peggy
+++ b/mpidl.peggy
@@ -19,7 +19,7 @@
 method :: Method
   = "inherit" identifier { InheritName $1 }
   / "inherit" "*" { InheritAll }
-  / "inherit"? ftype identifier "(" (field , ",") ")"
+  / "inherit"? rtype identifier "(" (field , ",") ")"
     { Function (isJust $1) $3 $2 $4 }
 
 field :: Field
@@ -30,6 +30,10 @@
   = ftypeNN "?" { TNullable $1 }
   / ftypeNN
 
+rtype :: Maybe Type
+  = "void" { Nothing }
+  / ftype { Just $1 }
+
 ftypeNN :: Type
   = "byte"   { TInt True  8  }
   / "short"  { TInt True  16 }
@@ -44,7 +48,6 @@
   / "bool"   { TBool }
   / "raw"    { TRaw }
   / "string" { TString }
-  / "void"   { TVoid }
   / "object" { TObject }
 
   / "list" "<" ftype ">" { TList $1 }
diff --git a/msgpack-idl.cabal b/msgpack-idl.cabal
--- a/msgpack-idl.cabal
+++ b/msgpack-idl.cabal
@@ -1,5 +1,5 @@
 name:                msgpack-idl
-version:             0.2.0
+version:             0.2.1
 synopsis:            An IDL Compiler for MessagePack
 description:         An IDL Compiler for MessagePack <http://msgpack.org/>
 homepage:            http://msgpack.org/
@@ -21,12 +21,12 @@
 
 library
   build-depends:       base             == 4.*
-                     , bytestring       == 0.9.*
-                     , text             == 0.11.*
+                     , bytestring       >= 0.9
+                     , text             >= 0.11
                      , shakespeare-text == 1.0.*
                      , blaze-builder    == 0.3.*
-                     , template-haskell >= 2.5 && < 2.8
-                     , containers       == 0.4.*
+                     , template-haskell >= 2.5 && < 2.9
+                     , containers       >= 0.4
                      , filepath         >= 1.1 && < 1.4
                      , directory
                      , msgpack          == 0.7.*
@@ -43,6 +43,7 @@
                        Language.MessagePack.IDL.CodeGen.Php
                        Language.MessagePack.IDL.CodeGen.Python
                        Language.MessagePack.IDL.CodeGen.Ruby
+                       Language.MessagePack.IDL.CodeGen.Erlang
                        Language.MessagePack.IDL.Internal
                        Language.MessagePack.IDL.Parser
                        Language.MessagePack.IDL.Syntax
@@ -52,8 +53,8 @@
   main-is:             main.hs
 
   build-depends:       base      == 4.*
-                     , directory >= 1.0 && < 1.2
-                     , cmdargs   == 0.9.*
+                     , directory >= 1.0
+                     , cmdargs   == 0.10.*
                      , peggy     == 0.3.*
                      , msgpack-idl