Hi there,

thank you all for your help with regards to the integer addition question that i asked yesterday it was very good in clarifying my ideas. However i would now like to ask for your expert help once again.

Basically i have a list of 16 tuples of 12 elements each, each tuple representing a train station - the tuple takes the form

station = [string, int, int, bool, bool, bool, bool, bool, bool, boo, bool, bool]

Basically i have a list called victoria line which is a list of 16 stations. What i want to do is access an element of the list so i can check and output the value that it holds. I'll include all my code below so you can see what i mean more as well as the attempt that i have made to do just that - its the bit called bakerloo!

import Prelude

type Element0 = String
type Element1 = Int
type Element2 = Float
type Element3 = Bool
type Element4 = Bool
type Element5 = Bool
type Element6 = Bool
type Element7 = Bool
type Element8 = Bool
type Element9 = Bool
type Element10 = Bool
type Element11 = Bool

type Station = [ (Element0, Element1, Element2, Element3, Element4, Element5, Element6, Element7, Element8, Element9, Element10, Element11) ]

victoriaLine :: Station

victoriaLine = [ ("Walthamstow Central", 1, 0, False, True, False, False, False, False, False, False, False),
          ("BlackHorse Road", 2, 3.0, False, True, False, False, False, False, False, False, False),
          ("Tottenham Hale", 3, 3.3, False, True, False, False, False, False, False, False, False),
       ("Seven Sisters", 4, 3, False, True, False, False, False, False, False, False, False),
              ("Finsbury Park", 5, 4.0, False, True, False, False, False, False, False, False, True),
       ("Highbury and islington", 6, 4.0, False, True, False, False, False, False, False, False, False),
              ("Kings Corss And St Pancras", 7, 3.3, False, True, False, True, False, False, True, True, True),
              ("Euston", 8, 1.3, False, True, False, False, False, False, False, True, False),
               ("Warren Street", 9, 2.0, False, False, False, False, False, False, False, True, False),
              ("Oxford Circus", 10, 1.45, True, False, True, False, False, False, False, False, False),
              ("Green Park", 11, 2.0, False, False, False, False, False, True, False, False, True),
              ("Victoria", 12, 2.3, False, True, False, False, True, True, False, False, False),
              ("Pimlico", 13, 1.0, False, False, False, False, False, False, False, False, False),
               ("Vauxhall", 14, 1.45, False, True, False, False, False, False, False, False, False),
              ("Stockwell", 15, 1.3, False, False, False, False, False, False, False, True, False),
              ("Brixton", 16, 2.0, False, True, False, False, False, False, False, False, False) ]
  

mainMenu :: IO()
mainMenu = do
  putStr"\n"
  putStr"Welcome To the Victoria Line Timetable System\n"
  putStr"Please Make A Choice from those Listed Below\n\n"
  putStr"Detail Station Information = stationMenu\n"
  putStr"For All Stations that link to the Bakerloo Line = Bakerloo\n"
  putStr"For All Stations that link to British Rail Services = British\n"
  putStr"For All Stations that link to the Central Line = Central\n"
  putStr"For All Stations that link to the Circle Line = Circle\n"
  putStr"For All Stations that link to the District Line = District\n"
  putStr"For All Stations that link to the Jubilee Line = Jubilee\n"
  putStr"For All Stations that link to the Metropolitan Line = Metropolitan\n"
  putStr"For All Stations that link to the Northern Line = Northern\n"
  putStr"For All Stations that link to the Piccadilly Line = Piccadilly\n"
  return()
  

stationMenu::IO()
stationMenu = do
  putStr"\n"
  putStr"Please Select The station You are located at\n\n"
  putStr"Walthamstow Central\n"
  putStr"BlackHorse Road\n"
  putStr"Tottenham Hale\n"
  putStr"Seven Sisters\n"
  putStr"Finsbury Park\n"
  putStr"Higbury and Islington\n"
  putStr"Kings Cross and St Pancras\n"
  putStr"Euston\n"
  putStr"Warren Street\n"
  putStr"Oxford Circus\n"
  putStr"Green Park\n"
  putStr"Victoria\n"
  putStr"Pimlico\n"
  putStr"Vauxhall\n"
  putStr"Stockwell\n"
  putStr"Brixton\n"

lineMenu::IO()
lineMenu = do
  putStr"\n"
  putStr"Please Select The Line you wish to connect to\n"
  putStr"Bakerloo Line = nrBakerloo\n"
  putStr"British Rail = nrBritish\n"
  putStr"Central Line = nrCentral\n"
  putStr"Circle Line = nrCircle\n"
  putStr"District Line = nrDistrict\n"
  putStr"Jubilee Line = nrJubillee\n"
  putStr"Metropolitan Line = nrMetropolitan\n"
  putStr"Northern Line = nrNorthern\n"
  putStr"Piccadilly Line = nrPicadilly\n"

bakerloo :: Station->Element0->[Element3]
bakerloo dBase findIt = do [ element3 | (element0, element1, element2, element3, element4, element5, element6, element7, element8, element9, element10, element11) <- dBase, element0 == findIt ]
    
stops:: Int->Int->Int
stops x y = x-y

main = do
 mainMenu
 putStr"\n\nTo Calculate the number of stops between your location and destination enter stop location destination\n"
 putStr"e.g. Stops 4 14\n"
 return()

So there it is - any help you can give would be great.

Thanks for all your responses yesterday.

Neil