Here’s a reminder of the predicates you must implement. See earlier slides in this assignment for details.
• hand_value (Hand, Startcard, Value)
Value (an integer) is the total cribbage point value of Hand when Star tcard is the start card. Hand is represented as a list of 4 card terms, and Startcard is a single card term. A card term is a term card (Rank, Suit), where Rank is either an integer between 2 and 10, or one of ace, jack, queen, or king, and Suit is one of clubs, diamonds, hearts, or spades. Your code need only work when Hand and Startcard are ground.
• select_hand Cards, Hand, Cribcards)
Cards is a list of the 5 or 6 cards dealt to a player at the start of a hand. Hand is a list of 4 of those cards to be kept to form the players hand, and Cribcards is a list of the cards not kept (to be placed in the crib). The cards to be kept in the hand should be chosen to maximize the expected value of the hand over all possible start cards. Since the start card is not known when the hand is chosen, you cannot be sure to choose the best hand. However the expected value of the hand is the average value of the hand over all possible start cards (Cribcards and Hand cards are not possible start cards). This predicate need only work when Cards is a ground list of card terms.
The objective of this project is to practice and assess your understanding of logic programming and Prolog. You will write code to perform the major parts of a cribbage playing program.
Cribbage is a very old card game, dating to early 17th century England. There are 2, 3, and 4 handed versions of the game. The object of the game is to be the first player to reach 121 points. Game play begins with the dealer dealing each player 6 cards (in a 2-player game) or 5 cards (in a 3 or 4 player game). In a 3 player game, the dealer also deals one card to a separate hand called the crib or box. Each player then chooses 1 or 2 cards to discard, keeping 4 and putting the discarded cards in the crib or box, which forms a second 4-card hand for the dealer. Next the player preceding the dealer cuts the deck to select an extra card, called the start card. If the start card is a Jack, the dealer immediately scores 2 points.
The hand then proceeds to the play, wherein the players take turns playing cards from their hands face up in front of them. The play will not be part of this project, so we will not discuss it further.
Following the play comes the show, where each player in turn, beginning with the player after the dealer, establishes the value of her hand. For this phase, the start card is usually considered as part of each player’s hand, so each player establishes the value of a 5 card hand. Points are scored for certain combinations of cards according to the following rules:
• (15s) 2 points are scored for each distinct combinations of cards that add to 15. For this purpose, an ace is counted as 1, and a jack, queen or king are counted as 10, and other cards count as their face value. For example, a hand with a 2, 3, 5, 10, and king scores 8 points: 2 points each for 2+3+10, 2+3+king, 5+10, and 5+king.
• (Pairs) 2 points are scored for each pair. With 3 of a kind, there are 3 different ways to make a pair, so 3 of a kind scores 6 points. Similarly, 4 of a kind scores 12 points for the 6 possible pairs.
• (Runs) 1 point is scored for each card in a run of 3 or more consecutive cards (the suits of these cards need not be the same). For example, a 2, 6, 8, and 9, with a 7 as the start card scores 4 points for a 4 card run. It also scores a further 6 points for 15s (6+9, 7+8, and 2+6+7).
• (Flushes) 4 points is scored if all the cards in the hand are of the same suit. 1 further point is scored if the start card is also the same suit. Note that no points are scored if 3 of the hand cards, plus the start card, are the same suit.
• (“One for his nob”) 1 point is scored if the hand contains the jack of the same suit as the start card.
All of these points are totalled to find the value of a hand. For example (using A for ace, T for 10, J for jack, Q for queen, and K for king, and &, *, w, and • as clubs, diamonds, hearts, and spades):
Following the show of each player’s hand, the dealer counts the crib as a second hand, claiming any points therein.
Finally, the player following the dealer collects the cards, becoming dealer for the next hand. Play proceeds this way until one player reaches 121 points.
Please see the rules of cribbage for a more complete description of the game. However, what is presented above will be enough to complete the project.
1. It is easier to look for pairs and runs in a hand if it is sorted first, with the start card included. Even 15s are slightly easier to compute when the hand is sorted. However, the start card must not be confused with the cards from the hand when looking for a flush or “one for his nob.”
2. This is easier still if the hand is represented as a sorted list of pairs of rank and number of occurrences of that rank. Note that pairs, runs, and 15s depend only on ranks, not on suits.
3. Note that Prolog’s built-in sort predicates will not sort card terms correctly. You can either transform the representation of cards and use the built-in sort predicate or write your own sort. The easiest way is probably to convert ace to 1, jack to 11, and so on, and then sort. The built-in predicate msort/2 will sort without removing duplicates (sort/2 does remove duplicates).
4. Feel free to use your hand_value/3 code, or parts of it, in implementing select_hand/3.
5. To choose the cards to make up your hand, you can consider the 15 4-card hands you can select from 6 cards, determine their hand_values, and choose the best of these.
6. You can improve on this by considering what the start card may bring to your hand. This will on average do a better job of choosing the best hand. For this, you should consider, for each of the 15 possible hands, the 46 possible start cards and the value it would give your hand. The average of these 46 possibilities would be the number of points you would expect on average to get from that choice of hand. Then simply select the hand with the greatest expected value.