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{-# LANGUAGE CPP, TypeFamilies, MultiParamTypeClasses, FunctionalDependencies,
FlexibleContexts, FlexibleInstances, UndecidableInstances, OverlappingInstances,
TypeSynonymInstances, GeneralizedNewtypeDeriving #-}
-----------------------------------------------------------------------------
-- |
-- Module : HSX.XMLGenerator
-- Copyright : (c) Niklas Broberg 2008
-- License : BSD-style (see the file LICENSE.txt)
--
-- Maintainer : Niklas Broberg, niklas.broberg@chalmers.se
-- Stability : experimental
-- Portability : requires newtype deriving and MPTCs with fundeps
--
-- The class and monad transformer that forms the basis of the literal XML
-- syntax translation. Literal tags will be translated into functions of
-- the GenerateXML class, and any instantiating monads with associated XML
-- types can benefit from that syntax.
-----------------------------------------------------------------------------
module T4809_XMLGenerator where
import Control.Applicative
import Control.Monad
import Control.Monad.Trans
import Control.Monad.Cont (MonadCont)
import Control.Monad.Error (MonadError)
import Control.Monad.Reader(MonadReader)
import Control.Monad.Writer(MonadWriter)
import Control.Monad.State (MonadState)
import Control.Monad.RWS (MonadRWS)
import Control.Monad (MonadPlus(..),liftM)
----------------------------------------------
-- General XML Generation
-- | The monad transformer that allows a monad to generate XML values.
newtype XMLGenT m a = XMLGenT (m a)
deriving (Monad, Functor, MonadIO, MonadPlus, MonadWriter w, MonadReader r,
MonadState s, MonadRWS r w s, MonadCont, MonadError e)
instance Monad m => Applicative (XMLGenT m) where
pure = return
(<*>) = ap
instance Monad m => Alternative (XMLGenT m) where
-- | un-lift.
unXMLGenT :: XMLGenT m a -> m a
unXMLGenT (XMLGenT ma) = ma
instance MonadTrans XMLGenT where
lift = XMLGenT
type Name = (Maybe String, String)
-- | Generate XML values in some XMLGenerator monad.
class Monad m => XMLGen m where
type XML m
data Child m
genElement :: Name -> [XMLGenT m [Int]] -> [XMLGenT m [Child m]] -> XMLGenT m (XML m)
genEElement :: Name -> [XMLGenT m [Int]] -> XMLGenT m (XML m)
genEElement n ats = genElement n ats []
-- | Embed values as child nodes of an XML element. The parent type will be clear
-- from the context so it is not mentioned.
class XMLGen m => EmbedAsChild m c where
asChild :: c -> XMLGenT m [Child m]
instance (MonadIO m, EmbedAsChild m c, m ~ n) => EmbedAsChild m (XMLGenT n c) where
asChild m = do
liftIO $ putStrLn "EmbedAsChild m (XMLGenT n c)"
a <- m
asChild a
instance (MonadIO m, EmbedAsChild m c) => EmbedAsChild m [c] where
asChild cs =
do liftIO $ putStrLn "EmbedAsChild m [c]"
liftM concat . mapM asChild $ cs
instance (MonadIO m, XMLGen m) => EmbedAsChild m (Child m) where
asChild c =
do liftIO $ putStrLn "EmbedAsChild m (Child m)"
return . return $ c
|
