Configurable (empty) → 0.1.0.0

raw patch · 4 files changed

+157/−0 lines, 4 filesdep +basesetup-changed

Dependencies added: base

Files

• Configurable.cabal +26/−0
• LICENSE +20/−0
• Setup.hs +2/−0
• src/Control/Configurable.hs +109/−0

@@ -0,0 +1,26 @@+-- Initial Configurable.cabal generated by cabal init.  For further +-- documentation, see http://haskell.org/cabal/users-guide/++name:                Configurable+version:             0.1.0.0+synopsis:            Declare types as Configurable then specialize them all in one place+description:         Declare types as Configurable then specialize them all in one place+homepage:            https://github.com/tel/Configurable+license:             MIT+license-file:        LICENSE+author:              Joseph Abrahamson <me@jspha.com>+maintainer:          Joseph Abrahamson <me@jspha.com>+copyright:           Joseph Abrahamson, 2012+category:            Control+build-type:          Simple+cabal-version:       >=1.8++library+  exposed-modules:     Control.Configurable+  -- other-modules:       +  build-depends:       base ==4.5.*+  hs-source-dirs:      src++source-repository head+  type:     git+  location: https://github.com/tel/Configurable.git

@@ -0,0 +1,20 @@+Copyright (C) 2012 Joseph Abrahamson++Permission is hereby granted, free of charge, to any person obtaining+a copy of this software and associated documentation files (the+"Software"), to deal in the Software without restriction, including+without limitation the rights to use, copy, modify, merge, publish,+distribute, sublicense, and/or sell copies of the Software, and to+permit persons to whom the Software is furnished to do so, subject to+the following conditions:++The above copyright notice and this permission notice shall be+included in all copies or substantial portions of the Software.++THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain

@@ -0,0 +1,109 @@+{-# LANGUAGE ExistentialQuantification,+             DeriveDataTypeable,+             MultiParamTypeClasses,+             FunctionalDependencies,+             ScopedTypeVariables,+             TupleSections #-}++module Control.Configurable (+  Configurable (..),+  Configuration,+  ConfiguredBy (..),+  ConfigMethod,+  doConfig, unsafeDoConfig, toConfigure, configureDefault+  ) where++import Data.Data+import Data.Monoid++-- | A 'Configurable' type is any type which should be specialized+-- from runtime configuration information. For instance, a record type+-- containing usernames and passwords for a database is probably+-- 'Configurable'. In principle, 'Configurable' types should be+-- distinguished from the functions/types/'ConfiguredBy' instances+-- they provide for.+class (Typeable a, Show a, Monoid a) => Configurable a where+  toConfiguration :: a -> Configuration+  toConfiguration = Configuration+  fromConfiguration :: Configuration -> Maybe a+  fromConfiguration (Configuration a) = cast a++  -- | A wildcard deconstructor on lists of 'Configuration's. After a+  -- list of 'Configuration's has been generated by either 'doConfig'+  -- or 'unsafeDoConfig', 'getConfig' is a typesafe destructor which+  -- can be used to filter the result for application to other+  -- functions. The default implementation relies on the 'Monoid'+  -- instance of the 'Configurable' to combine configurations.+  getConfig :: [Configuration] -> Maybe a+  getConfig cs = mconcat (map fromConfiguration cs)++-- | A 'Configuration' is an opaque wrapper around an existentially+-- typed 'Configurable'. +data Configuration = forall a. Configurable a => Configuration a+                   deriving Typeable++instance Show Configuration where+  showsPrec p (Configuration a) = showsPrec p a++instance Configurable ()++-- | The default 'Monoid' instance of 'Configuration' is simply+-- left-annihilation. The 'mempty' just wraps the '()' type.+instance Monoid Configuration where+  mempty      = Configuration ()+  mappend a _ = a++-- | 'ConfiguredBy' is a convenience class allowing specification of+-- which kinds of 'Configurable's are needed for other types.+class Configurable b => ConfiguredBy a b | a -> b where+  -- | The default implementation relies on the functional dependency+  -- in the type and the 'Monoid' instance method 'mempty' of the+  -- 'Configurable'.+  confs :: a -> [Configuration]+  confs _ = [toConfiguration (mempty :: b)]++-- | 'ConfigMethod' is an opaque wrapper for methods to specialize+-- 'Configurations'.+data ConfigMethod = ConfigMethod { unConfigM :: [(Configuration, Bool)] }++-- | 'toConfigure' allows you to specify a specialization function for+-- any particular 'Configurable'. These are combinated together into a+-- large specialization routine which is then run via 'doConfig' or+-- 'unsafeDoConfig'.+toConfigure :: Configurable a => (a -> a) -> ConfigMethod -> ConfigMethod+toConfigure f = ConfigMethod . map ff . unConfigM+  where ff (z, configured) =+          case fromConfiguration z of+            Just a  -> (toConfiguration (f a), True)+            Nothing -> (z, configured)++-- | Introduce a new 'Configurable' based on its 'mempty' method.+configureDefault :: Configurable a => (a -> a) -> Configuration+configureDefault f = toConfiguration (f mempty)++-- | Given some 'Configuration' goals, use 'ConfigMethod's to+-- specialize a '[Configuration]'+doConfig :: [[Configuration]]+            -> (ConfigMethod -> ConfigMethod)+            -> Either [Configuration] [Configuration]+doConfig = flip runConfig++-- | An auxilary function for definine 'doConfig'.+runConfig :: (ConfigMethod -> ConfigMethod)+            -> [[Configuration]]+            -> Either [Configuration] [Configuration]+runConfig f = ret . unConfigM . f . ConfigMethod .  map (,False) . concat+  where ret cs = let unconfigured = filter (not . snd) cs+                 in if null unconfigured+                    then Right (map fst cs)+                    else Left (map fst unconfigured)++-- | Given some 'Configuration' goals, use 'ConfigMethod's to+-- specialize a '[Configuration]', but if any goals are never+-- specialized then fail immediately!+unsafeDoConfig :: [[Configuration]] -> (ConfigMethod -> ConfigMethod) -> [Configuration]+unsafeDoConfig cs f = go cs+  where+    go = map check . unConfigM . f . ConfigMethod .  map (,False) . concat+    check (c, True) = c+    check (c, False) = error $ "Required " ++ show c