Useless.hs

--
-- Skeleton for Salsa interpreter
-- To be used at the exam for Advanced Programming, B1-2013
--

module SalsaInterp
       -- (Position, interpolate, runProg)
where

import SalsaAst
import Gpx

--
-- The function interpolate
--

type Position = (Integer, Integer)
interpolate :: Integer -> Position -> Position -> [Position]
interpolate = undefined

--
-- Define the types Context and SalsaCommand
--

type View = (Ident, Int, Int)

data Context = Context { env   :: Env
                       , state :: State }
               deriving Show

data Env = Env { views  :: [(Ident, View)]
               , groups :: [(Ident, [Ident])]
               , shapes :: [(Ident, Int)]
               } deriving Show

data State = State { positions :: [(Int, Position)] }
           deriving Show

initialContext = Context env st
  where env = Env [] [] []
        st  = State []

newtype SalsaCommand a = SalsaCommand { runSC :: Context -> (a, Context) }

instance Monad SalsaCommand where
  return x = SalsaCommand $ \ context -> (x, context)
  (SalsaCommand ma) >>= f = SalsaCommand $ \ context ->
    let (a, context') = ma context
        SalsaCommand mb = f a
        (b, context'') = mb context' { env = env context }
    in (b, context'' { env = env context })

-- functions for manipulating the context

move :: Int -> Position -> SalsaCommand ()
move i pos = SalsaCommand $ \c -> ((), let c' = c { state = s' }
                                           s' = (state c) { positions = (i, pos) : positions (state c) }
                                       in c')

moveTwice i pos = do
  messWithEnv
  move i pos
  move i pos

messWithEnv :: SalsaCommand ()
messWithEnv = SalsaCommand $ \c -> ((), c { env = Env [] [] [("foo", 1)] })

local :: Context -> SalsaCommand a -> SalsaCommand ()
local con cmd = SalsaCommand $ \_ -> ((), con) ...

-- getEnv :: SalsaCommand Env
-- getEnv = SalsaCommand $ \ context -> (env context, context)

-- getState = SalsaCommand $ \ context -> (state context, context)

-- getShapes = do
--   env <- getEnv
--   return (shapes env)

-- getActiveViews = do
  

--
-- Define the function command
--

-- command :: Command -> SalsaCommand ()
-- command (Move ids pos) = do
--   env <- getEnv
--   let sh = shapes env

--
-- Define the type Salsa
--

-- data Salsa a = ...


--
-- Define the functions liftC, definition, and defCom
--

-- liftC :: SalsaCommand a -> Salsa a

-- definition :: Definition -> Salsa ()
-- definition (Def def) = ...
-- definition (Com cmd) = command cmd

defCom :: DefCom -> Salsa ()
defCom (Def def) = 

program :: Program -> Salsa ()
program dcs = mapM_ defCom dcs

--
-- Define the function runProg
--

-- runProg :: Integer -> Program -> Animation