[eclipse-clp-users] minlist /2 in a Point list

From: Igor Kondrasovas <igor_at_inovativatec.com>
Date: Wed, 19 May 2010 00:50:24 -0300


I would like to use the the bb_min /3 predicate to find the lowest “Cost”
solution available in my search / 6 results:


The search is: search(XYs, 0, first_fail, indomain_split, complete, []),


XYs is a list of points (X,Y) elements and the cost is equals to the maximum
X value on the entire list, so my goal is to minimize this cost.


I would like to know if I could use maxlist /2 to define the cost value or
if there is any built-in predicate I could use, since it is not a simple
scalar numeric list (only X value is considered). 


If not, my question would be how to define the Cost variable. Iterating over
the list and find the maximum value sees not correct, since the search still
did not happened yet.  


Here is the way Im defining the predicate. In fact the code hangs when the
bb_min is used.


solve(Points, Polygons, NFs, Width, Length) :-

                ( foreach((X,Y),Points), param(Width, Length),
fromto(XYs,[X,Y|XYs1],XYs1,[]) do

                               X :: 0..Length,

                               Y :: 0..Width,




                %Define sheet boundaries constraints

                sheetBounds(Points, Polygons, Width, Length),


                %Define non overlap constraints

                ( foreach(Point1,Points) * foreach(Point2,Points),



                    ( Point1 \== Point2 ->

                               NFs1 = [NF|NFs2],

                        outside_polygon1(Point1, Point2, NF)


                               NFs1 = NFs2




                %Cost calculation

                ( foreach((X,_),Points), fromto(Xs,[X|Xs1],Xs1,[]) do



                maxlist(Xs, Cost),

                bb_min(search(XYs, 0, first_fail, indomain_split, complete,
[]), Cost, _),



I have a feeling that something is wrong on the Cost calculation, but I
could not identify.


I appreciate any help,





Igor Kondrasovas

Project Management

Inovativa Tecnologia


+55 47 3027-6442

+55 47 8839-1592

Received on Wed May 19 2010 - 03:50:33 CEST

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