[commit: haskeline] master: Don't use MonadState to expose the History API. (71bbf20)

[Ian Lynagh]

Repository : ssh://darcs.haskell.org//srv/darcs/packages/haskeline

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/71bbf20f717083f8e1acf878b97925f309b92f74

>---------------------------------------------------------------

commit 71bbf20f717083f8e1acf878b97925f309b92f74
Author: Judah Jacobson <judah.jacobson at gmail.com>
Date:   Fri Feb 24 23:46:53 2012 +0000

    Don't use MonadState to expose the History API.
    
    Instead, provide explicit get/put/modifyHistory actions.
    This makes it easier to use InputT in a stack of monad transformers.

>---------------------------------------------------------------

 System/Console/Haskeline.hs        |   15 ++++++++++++++-
 System/Console/Haskeline/InputT.hs |   20 ++++++++++++++------
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/System/Console/Haskeline.hs b/System/Console/Haskeline.hs
index 419d91a..715b382 100644
--- a/System/Console/Haskeline.hs
+++ b/System/Console/Haskeline.hs
@@ -61,6 +61,12 @@ module System.Console.Haskeline(
                     defaultPrefs,
                     runInputTWithPrefs,
                     runInputTBehaviorWithPrefs,
+                    -- ** History
+                    -- $history
+                    getHistory,
+                    putHistory,
+                    modifyHistory,
+                    -- * Additional submodules
                     module System.Console.Haskeline.Completion,
                     module System.Console.Haskeline.MonadException)
                      where
@@ -177,7 +183,7 @@ maybeAddHistory result = do
                         AlwaysAdd -> addHistory
                         IgnoreConsecutive -> addHistoryUnlessConsecutiveDupe
                         IgnoreAll -> addHistoryRemovingAllDupes
-               in modify (adder line)
+               in modifyHistory (adder line)
         _ -> return ()
 
 ----------
@@ -246,6 +252,13 @@ getPassword x = promptedInput
                      ]
     loop' = keyCommand loop
                         
+{- $history
+The 'InputT' monad transformer provides direct, low-level access to the user's line history state.
+
+However, for most applications, it should suffice to just use the 'autoAddHistory'
+and 'historyFile' flags.
+
+-}
 
 
 -------
diff --git a/System/Console/Haskeline/InputT.hs b/System/Console/Haskeline/InputT.hs
index 8dd031c..9129a91 100644
--- a/System/Console/Haskeline/InputT.hs
+++ b/System/Console/Haskeline/InputT.hs
@@ -14,7 +14,7 @@ import System.Console.Haskeline.Term
 import System.Directory(getHomeDirectory)
 import System.FilePath
 import Control.Applicative
-import qualified Control.Monad.State as State
+import Control.Monad (liftM, ap)
 import System.IO
 
 -- | Application-specific customizations to the user interface.
@@ -47,18 +47,26 @@ newtype InputT m a = InputT {unInputT :: ReaderT RunTerm
                                 MonadReader (Settings m), MonadReader RunTerm)
 
 instance Monad m => Functor (InputT m) where
-    fmap = State.liftM
+    fmap = liftM
 
 instance Monad m => Applicative (InputT m) where
     pure = return
-    (<*>) = State.ap
+    (<*>) = ap
 
 instance MonadTrans InputT where
     lift = InputT . lift . lift . lift . lift . lift
 
-instance Monad m => State.MonadState History (InputT m) where
-    get = get
-    put = put
+-- | Get the current line input history.
+getHistory :: Monad m => InputT m History
+getHistory = get
+
+-- | Set the line input history.
+putHistory :: Monad m => History -> InputT m ()
+putHistory = put
+
+-- | Change the current line input history.
+modifyHistory :: Monad m => (History -> History) -> InputT m ()
+modifyHistory = modify
 
 -- for internal use only
 type InputCmdT m = StateT Layout (UndoT (StateT HistLog (StateT KillRing