Haskell data type list - haskell

Question

I am new to Haskell, and I want to make a program with lists. I want to read from keyboard next element, and append everything to my existing list. Because I used data types, I don't know how to add a new car with all those details, in my list named cars.
I know that sequence let ls = name:model:color:year:price:coin:[cars] is wrong and I have no ideea how to make it work. Can anyone give me an ideea about what can I do here please?
type Name = String
type Model = String
type Color= String
type Year = String
type Price = String
type Coin = String
data Car = Car String String String String String String deriving (Show)
cars :: [Car]
cars = [Car "Range Rover" "Sport Supercharged" "Blue" "2015" "85790" "$" , Car "BMW" "4-Series" "Black" "2014" "65489" "$"]
main = do
putStrLn "Car details "
putStr "Name: "
name <- getLine
putStr "Model: "
model <- getLine
putStr "Color: "
color <- getLine
putStr "Year: "
year <- getLine
putStr "Price: "
price <- getLine
putStr "Coin: "
coin <- getLine
let ls = name:model:color:year:price:coin:[cars]
putStrLn (show ls)

Answer 1

First I'd recommend you actually use those type synonyms, if you define them at all:
data Car = Car Name Model Color Year Price Coin
deriving (Show)
Note that this is completely equivalent to declaring all fields String (because Model and String are just different names for exactly the same type), it's just clearer to read. Even clearer might be if you used record fields for such a type, but that wouldn't make a difference here.
Now to “create” a new car from some string properties, you want to not concatenate these properties to a list. Instead, just use the Car constructor and prepend a single car to the list.
main = do
putStrLn "Car details "
putStr "Name: "
name <- getLine
...
let cars' = Car name model color year price coin : cars
print cars'
In case you wonder: Car foo bar baz : cars is the same as (Car foo bar baz) : (cars). In fact, Car is just used like any other function here; you could also define a helper function
redCar :: Name -> Model -> Year -> Price -> Coin -> Car
redCar n m y p c = Car n m "red" y p c
and then write
print $ redCar name model year price coin : cars
OTOH, [cars] is not a list of cars that you could prepend another car to; rather it's a list with a single element (and that element is a list of cars).
A different subject is how you update stuff in general, in Haskell. ErikR adresses how this can be done with recursion; I'd note that you can also have proper mutable variables in Haskell IO code. We generally avoid working in IO as much as possible, but if you actually write an interactive application then it's sensible enough:
import Data.IORef
main = do
knownCars <- newIORef cars
putStrLn "Car details "
...
modifyIORef knownCars $ Car name model color year price coin
print =<< readIORef cars
Then you can follow this with
putStrLn "Details of another car:"
...
modifyIORef knownCars $ Car name2 model2 color2 year2 price2 coin2
and actually have both cars added. Of course this only makes sense if the whole program is actually running in a loop. (“Loop” still meaning recursion, in fact.)

Answer 2

As you probably have been told, Haskell "variables" are not mutable. That means you have to explicitly pass state around as a parameter in your loop.
For example, this is a loop which will repeatedly ask the user for a color:
loop1 = do putStrLn "Enter a color: "
color <- getLine
loop1
However, the users's input is not "saved" anywhere. The next step is to keep track of all of previous input as a parameter to the looping function:
loop2 colors = do putStrLn $ "Previous colors: " ++ show colors
putStrLn "Enter a color: "
color <- getLine
loop2 (color:colors)
Hopefully this helps.