Default.hs

-----------------------------------------------------------------------------
--
-- Module      :  IDE.Utils.Default
-- Copyright   :  (c) Juergen Nicklisch-Franken (aka Jutaro)
-- License     :  GNU-GPL
--
-- Maintainer  :  Juergen Nicklisch-Franken <jnf at arcor.de>
-- Stability   :  experimental
-- Portability :  portable
--
-- | Module for default values of a data type
--
------------------------------------------------------------------------------

module IDE.Utils.Default (
    Default(..)
) where

--
-- | A class for providing default values for certain types of editors
--
class Default alpha where
    getDefault      ::   alpha

instance Default Int where
    getDefault      =   1

instance Default alpha  => Default (Either alpha beta) where
        getDefault  =   Left(getDefault)

instance (Default alpha, Default beta) => Default (alpha, beta) where
        getDefault  =   (getDefault,getDefault)

instance Default [alpha] where
        getDefault  =   []

instance Default (Maybe alpha) where
    getDefault      =   Nothing