-----------------------------------------
-- Programm "Routenberechnung"  --
-----------------------------------------
module Route where
import System   -- stellt getArgs :: IO [String] bereit


------------------------
-- Die Hauptfunktion  --
------------------------    

main :: IO ()
main =  do ...



{-
readArguments :: IO (Town,Town,String)
readRoads     :: String -> IO [Road]
route         :: [Road] -> Town -> Town -> Route
formatRoute   :: Route  -> String
-}






-----------------------------------------------------
-- Teilschritt 1: Einlesen der Argumente           --
-----------------------------------------------------

-- vordefiniert in Bibliothek System
-- getArgs :: IO [String] 

type Town = String

readArguments :: IO (Town,Town,String)
readArguments =  do ...
















-----------------------------------------------
-- Teilschritt 2: Einlesen der Straßeninfos  --
-----------------------------------------------

type Road = (Town,Town,Int) 
readRoads :: String -> IO [Road]
readRoads dat =  do ...






















-----------------------------------------------
-- Teilschritt 3: Formatierung der Ausgabe   --
-----------------------------------------------

type Route = (Town, Town, Int, [(Town,Int)])
           -- von - nach - Laenge - Verlauf

formatRoute :: Route -> String
formatRoute (from, to, dist, stages) 
  = ...













----------------------------------------------------
-- Teilschritt 4: Berechnung der kürzesten Route  --
----------------------------------------------------

route :: [Road] -> Town -> Town -> Route
route roads from to ...


startP, endP :: Road -> Town
startP (from, to, dist) = from
endP   (from, to, dist) = to

better :: Route -> Route -> Route
better r1@(from1,to1,dist1,stages1) 
       r2@(from2,to2,dist2,stages2)
   ... 
   where lr1 = length stages1
         lr2 = length stages2

best :: [Route] -> Route 
...


joinRoutes :: Route -> Route -> Route 
...


road2Route :: Road -> Route
...


bothWays :: [Road] -> [Road]
...






-- Routenverfolgung zu Debugging-Zwecken
debugmain :: Town -> Town -> String -> IO ()
debugmain from to datei 
       =  do -- (from,to,datei) <- readArguments
             roads           <- readRoads datei
             putStr $ unlines $ map show (debugroute roads from to)



debugroute :: [Road] -> Town -> Town -> [Road] 
debugroute roads from to | from  == to = []
debugroute roads from to 
   = concat [road : debugroute roads (endP road) to
         | road <- bothWays roads, 
           startP road == from]