Although I am familiar with Prolog, I'm not very familiar with core.logic yet :-( But maybe I can provide you an explanation of that Prolog code and you can derive the core.logic implementation by yourself...
All clauses you provided define one predicate, move(), which has two arguments and both of them are lists of four variables (e.g. [A,B,C,D] is also a list of four variables). This predicate defines a relationship between those two lists. Given the first list with provided concrete values, the predicate will assign all possible values to the elements of the second list. These values must fulfill the contract, defined by the body of the predicate... E.g. let's take this one: --------------- move([X, Y, Xmax, Ymax], [A, B, Xmax, Ymax]) :- X + 1 < Xmax, Y + 2 < Ymax, A is X + 1, B is Y + 2. --------------- This basically means, that if you call: "move([1, 2, 5, 6], [A, B, Xmax, Ymax])." you will be given all the possible values of A, B, Xmax and Ymax such that this will hold true: X + 1 < Xmax && Y + 2 < Ymax && A = X + 1 && B = Y + 2 concretely, you will receive the values: A = 2, B = 4, Xmax = 5, Ymax = 6. (The last two are the same that were provided when calling the predicate.) The last information is, that there is a "logical OR" between all the 8 provided "move()" expressions, so that whichever of them can found at least one valid solution, it will be used. It's like as if they were the lines of a "conde" in core.logic. I hope that this can help you at least a little. If you have any questions, just ask ;-) Marek. P.S. My apologize to all the Prolog programmers here for simplified (and not always correct) Prolog terminology... On Monday, June 11, 2012 12:25:49 PM UTC+2, Jim foo.bar wrote: > > I managed to find this piece of prolog code in > http://bkraabel.free.fr/pages/kmoves_pl.html#top > of page <http://bkraabel.free.fr/pages/kmoves_pl.html#top%20of%20page>but I > don't know how to read it! Can anyone help me translate that to > core.logic so i have a starting point? checkers also move similarly to > knights (but just one position at a time)... > > % The following 8 moves define all the possible moves a knight > % may make on a chess board, without leaving the chess board. The > % size of the chess board is given by (Xmax, Ymax). > > move([X, Y, Xmax, Ymax], [A, B, Xmax, Ymax]) :- > X + 1 < Xmax, > Y + 2 < Ymax, > A is X + 1, > B is Y + 2. > > move([X, Y, Xmax, Ymax], [A, B, Xmax, Ymax]) :- > X + 2 < Xmax, > Y + 1 < Ymax, > A is X + 2, > B is Y + 1. > > move([X, Y, Xmax, Ymax], [A, B, Xmax, Ymax]) :- > X + 2 < Xmax, > Y - 1 >= 0, > A is X + 2, > B is Y - 1. > > move([X, Y, Xmax, Ymax], [A, B, Xmax, Ymax]) :- > X + 1 < Xmax, > Y - 2 >= 0, > A is X + 1, > B is Y - 2. > > move([X, Y, Xmax, Ymax], [A, B, Xmax, Ymax]) :- > X - 1 >= 0, > Y - 2 >= 0, > A is X - 1, > B is Y - 2. > > move([X, Y, Xmax, Ymax], [A, B, Xmax, Ymax]) :- > X - 2 >= 0, > Y - 1 >= 0, > A is X - 2, > B is Y - 1. > > move([X, Y, Xmax, Ymax], [A, B, Xmax, Ymax]) :- > X - 2 >= 0, > Y + 1 < Ymax, > A is X - 2, > B is Y + 1. > > move([X, Y, Xmax, Ymax], [A, B, Xmax, Ymax]) :- > X - 1 >= 0, > Y + 2 < Ymax, > A is X - 1, > B is Y + 2. > > > Jim > > On 11/06/12 01:09, Jim - FooBar(); wrote: > > Hello everyone, > > I'm trying to decide if its worth writing the rules of chess/checkers > using core.logic or go down the conventional road but unfortunately I'm > inexperienced as far as core.logic goes. I mean I've played around for a > bit but nothing serious. > > What I want is NOT AI or anything like that...all I want is to encode the > rules of the game somehow so i can then pass a board and a piece to some > function that will be able to find all available moves that don't violate > the rules of the game - no picking the best move or anything like > that...just finding the legal moves efficiently...does this sound > reasonable? I'm surprised there are so little on-line resources on the > matter! > > if someone can explain the advantages and the disadvantages of of doing so > that would be fanatstic...Even better if someone can point me in the right > direction (some similar project perhaps). I really have no idea how to > start and its one of the few times g8ggle doesn't seem to help... > > thanks in advance... > > > Jim > > > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
