Ok I have to write a program that creats an ADT to store a set of cards that are imput so that i can use the command (a-card rank suit) and (rank card) (suit card) to firstly construct the card and then return its rank and suit. Unfortunately I am struggling alot with this and wondering if someone could prod me in the correct direction.


any and all prods greatly appreciated, as this is just giving me an error

Using this I can get (a-card) to return the correct value, how do I then get this value to be passed out of the procedure (i.e. so I can recall it and also use it for (card) ?

Thanks

Try defining accessor functions that return particular elements of the list using car and cdr.

There are no procedures in scheme, only functions. Whenever you say define, you are naming an expression that evaluates to something.

Hence, follow along:
(a-card 13 'spades) becomes
(make-card 13 'spades) becomes
(list 13 'spades) becomes
'(13 'spades)
The make-card and a-card functions do the same thing: take a rank and suit and return a card. Why not get rid of one of them?

I think you need to re-read your class notes about the difference between a list and a pair.

Personally, I would store the card as a pair:
(define make-card (lambda (rank suit) (cons rank suit)))
Or, using the shortcut syntax:
(define (make-card rank suit) (cons rank suit))

Now, you know that a card is a pair of '(rank . suit), so to get out the rank or suit you only need a new function get knows what a card looks like:
(define (rank card) (car card))
(define (suit card) (cdr card))

The purpose is to make it so that no one knows that a card is just a pair (or a list or something else). You know, because that is how you are storing it. But anyone else using your program only needs to know three functions:
make-card rank suit: return a card object
rank card: return the rank of a card object
suit card: return the suit of a card object

Hope this helps.

That is fantastic, however, the reason I was playing with a list was that I need to store 5 cards (a poker hand), would the best way be to make the pair and then store the pair in a list along with the other 5 then?

thanks again

Yes. A card is a single object. If you want a list of cards, then store a list of cards, not a list of suits and ranks.

Thereafter, you can get, say, the second card's suit with:
(suit (second dead-mans-hand))

Hope this helps.

The help so far has been fantastic, I now have the single cards working, and am working on constructing the hand, the a-hand function works fine, however the next thing is to impliment "(contents hand) - returns a list of card objects (as constructed by a-card in the hand."

Now i have no problem doing this as i could just simply put


That the correct way to do it you think?

Thanks again for all the help

*Edit* just tried this way and it is giving me an error of "wrong type in arg1" >.<
*Edit* Just removed the (Define (hand c1 c2 .....) statement and simply type (contents (a-hand c1 c2 c3 c4 c5)) and it works fine

Just wondering though, how can i seperate the two things in a card in a hand? would it be

Since a "hand" object is a list of cards, and you want to get a list of cards from a hand, all you need to do is return the hand:
(define (contents hand) hand)
Now, if a "hand" object were something else, you'd need to do some work to turn it into a list...


Exactly.

Is there anyway to sort a list of numbers (and words alphabetically) into order?

thanks

Of course. You'll need to read up on recursion.

There is a basic principle: if you have a list
(a b c d)
(which, if you remember, is really:
(a . (b . (c . (d . ()))))
and if you can do something to the car of the list (or a) and the cdr of the list (that is, the rest of the list: (b c d)),
then you can do something to the whole list.

Remember, your list is a list of 'card's. So you'll have to use the card ADT to get the rank of each card and compare its value.

Hope this gets you started. Using scheme (and other functional languages) require you to think pretty hard.