So... some clarifying questions: 1) What's the difference between BoolVarArgs and BoolVarArray?
2) Could you explain in more detail what ~ does? 3) Likewise, what does tt() do? 4) Under exactly what conditions does post() create a BoolVar? 5) How's the documentation coming along? Malcolm On 20/11/2008, at 6:30 PM, Mikael Zayenz Lagerkvist wrote: > On Thu, Nov 20, 2008 at 7:52 AM, Malcolm Ryan <[EMAIL PROTECTED] > > wrote: >> I'm not sure I understand that code. Would you mind explaining in >> more >> detail? > > First of all, the loops in the code looping through layers can be > ignored for exposition, since they are there to handle the cases when > cards are in the bottom, middle, or top of a pile of three cards. > Assume that we have two piles of card (X1, X2, X3) and (Y1, Y2, Y3) > where Xv and Xv are integer variables, and where X2 and Y2 have the > same function for purposes of the game. The values of the cards > represent when they are played (note that I mistranslated the > condition in my earlier post, X1 and Y1 should be exchanged, as should > X3 and Y3). Now the code can be simplified to > // cond is the condition for the symmetry > BoolVarArgs ba(4); > // Both cards played after the ones on top of them > ba[0] = post(this, ~(X2 < Y3)); > ba[1] = post(this, ~(Y2 < X3)); > // Both cards played before the ones under them > ba[2] = post(this, ~(Y1 < X2)); > ba[3] = post(this, ~(X1 < Y2)); > // Cond holds when all the above holds > BoolVar cond(this, 0, 1); > rel(this, BOT_AND, ba, cond); > > // If cond is fulfilled, then we can order the cards > // cond -> (X2 < Y2) > post(this, tt(!cond || ~(X2 < Y2))); > > The ba-array holds a set Boolean variables for reified relations, and > the rel-function takes the conjunction of these. The final post just > uses the standard unfolding of an implication since there is no > implication-operator. You can also use the implication-function > together with post to get it: > post(this, tt(imp(cond, ~(X2 < Y2)))); > > >> How do you do reified constraints in Gecode? > > By using the reified post-functions, such as > rel(this, x, IRT_LE, y, b); > with x and y integer variables and b a Boolean control variable. In > MiniModel expressions, you can use the unary tilde-operator to reify > an expression: > BoolVar b = post(this, ~(x < y)); > > Cheers, > Mikael > > -- > Mikael Zayenz Lagerkvist, http://www.ict.kth.se/~zayenz/ _______________________________________________ Gecode users mailing list [EMAIL PROTECTED] https://www.gecode.org/mailman/listinfo/gecode-users
