content: -----------------------------------------------------------------------------
  -- |
  -- Module      :  Distribution.Text
  -- Copyright   :  Duncan Coutts 2007
  --
  -- Maintainer  :  cabal-devel@haskell.org
  -- Portability :  portable
  --
  -- This defines a 'Text' class which is a bit like the 'Read' and 'Show'
  -- classes. The difference is that is uses a modern pretty printer and parser
  -- system and the format is not expected to be Haskell concrete syntax but
  -- rather the external human readable representation used by Cabal.
  --
  module Distribution.Text (
    Text(..),
    display,
    ) where
  
  import qualified Text.PrettyPrint          as Disp
  
  import Data.Version (Version(Version))
  import qualified Data.Char as Char (isDigit, isAlphaNum, isSpace)
  
  class Text a where
    disp  :: a -> Disp.Doc
  
  display :: Text a => a -> String
  display = Disp.renderStyle style . disp
    where style = Disp.Style {
            Disp.mode            = Disp.PageMode,
            Disp.lineLength      = 79,
            Disp.ribbonsPerLine  = 1.0
          }
  
  -- -----------------------------------------------------------------------------
  -- Instances for types from the base package
  
  instance Text Bool where
    disp  = Disp.text . show
  
  instance Text Version where
    disp (Version branch _tags)     -- Death to version tags!!
      = Disp.hcat (Disp.punctuate (Disp.char '.') (map Disp.int branch))
  