gistfile1.hs

{-# LANGUAGE ExistentialQuantification, DeriveDataTypeable #-}
module Main where

import Data.Typeable

data Highlighter cache syntax = SynHL {hlFocus :: Int -> cache -> cache}

data HLState syntax = forall cache. HLState !(Highlighter cache syntax) !cache

data BufferImpl syntax =
        FBufferData { hlCache :: !(HLState syntax) }
        deriving Typeable

focusAst ::  Int -> BufferImpl syntax -> BufferImpl syntax
focusAst r b@FBufferData {hlCache = HLState s@(SynHL {hlFocus = foc}) cache} = b {hlCache = HLState s (foc r cache)}

main = return ()