> import IOutilities(getCookedLine, trim)
> import Project2CSupport(leftCircularShift)


explain purpose, retrieve data from file, initiate interaction

> main =
>   do
>     putStr msgWelcome
>     carFile <- readFile "car.txt"
>     queryResults(lines carFile)


retrieve queries from keyboard and
send corresponding results to screen

> queryResults carData =
>   do
>     putStr msgEnterQuery
>     queryString <- getCookedLine
>     if trim queryString == endDataSignal
>       then
>         putStr msgQuit
>       else
>         do
>           putStr(unlines(
>             [msgReply] ++
>             [msgIndent ++ zipcode |
>              zipcode <- ownerZipcodes (words queryString) carData]++
>             [msgEmptyLine]))
>           queryResults carData


termination signal

> endDataSignal = "quit"


messages of interaction

> msgWelcome = unlines[msgEmptyLine,
>                      "Car-owner Zipcode Listings Service",
>                      "  (enter \"quit\" at any time to terminate)",
>                      msgEmptyLine]
> msgEnterQuery = unlines["Enter makes of cars of interest"] ++
>                 "all on one line, separated by spaces: "
> msgReply =
>   unlines[msgEmptyLine,
>           "Zipcodes on file of owners of all cars of interest:"]
> msgIndent = "  "
> msgQuit = unlines["Zipcode Service Terminated"]
> msgEmptyLine = ""


... put definitions of other functions here ...

deliver sequence containing zipcodes
of all owners who own cars of all makes listed in carMakes

> ownerZipcodes carMakes owners =
>   [(thirdFromLast . words) owner |
>    owner <- ownersOfAll carMakes owners]


deliver sequence containing all owners
who own cars of all makes listed in carMakes

> ownersOfAll carMakes =
>    foldr1 (.) [ownersOf make | make <- carMakes]


deliver all owners who own a car of given make

> ownersOf make owners =
>   [owner | owner <- owners,
>            elementOf make [(nextToLast . words) owner,
>                            (last . words) owner       ]]


elementOf x xs is True if x is an element of xs, False otherwise

> elementOf x xs  =  xs /= (remove x xs)


remove v xs is a sequence like xs,
but without any elements equal to v

> remove v xs = [x | x <- xs, x /= v]


Individual Project 2A
nextToLast[ ..., x, y, z] = y

> nextToLast xs = (head . rightCircularShift . rightCircularShift) xs


Individual Project 2B
nextToLast[ ..., x, y, z] = x

> thirdFromLast xs = (head . rightCircularShift .
>                       rightCircularShift . rightCircularShift) xs


Individual Project 2C
rightCircularShift[a, b, c, ..., x, y, z] = [z, a, b, c, ..., x, y]

> rightCircularShift xs = (reverse . leftCircularShift . reverse) xs


test variables

> carData = 
>   ["Karen A Thorson, 112 Main, St Paul MN 55102 Ford Saab",
>    "John Shadley,  1601 S Shepherd, Houston TX 77019   Volkswagen Buick",
>    "William J T Harris, 2300 S Vandalia Av, Tulsa OK 74135 Honda Toyota",
>    "The Noellerts, 6650 Beach Blvd, Buena Park CA 90622 BMW Audi",
>    "Kathleen O'Donnell, 401 N Wabash, Chicago IL 60611 Ford Buick",
>    "Alastair James, 3100 Mass Av NW, Washington DC 20008 Rolls-Royce none",
>    "Barbara Maler, 1946 N Hillside, Wichita KS 67208 Honda Honda",
>    "Ozalp Babaoglu, 1024 Ramona, Palo Alto CA 94301 Toyota Honda"]