Hello all,
I've been trying to learn Oz constraint programming. After some simple
examples I tried my hand at something "harder". However, I can't seem to
find a way to post a constraint that makes reference to a tuple. The
constraint problem to be solved is given a list of matches with each end of
the match having a colour, align the matches in a line such that all
adjacent ends have the same colour.
I tried also creating a local variable and using reified constraints. That
didn't work either as I think I'm a little over my head and mixing "=:" with
"==".
Any ideas on how to get this type of constraint working? Or how to
reformulate the problem?
Michal
============ file: Example.oz ====================
% The constraint to be posted is at the FIXME
functor
import
FD
Browser
Search
define
% Our matches, where each match has different coloured ends.
% Different colours represented by different numbers.
% Note that the matches are given in an order that provides a solution:
% 0---1 1---0 0---2 2---2 2---0
%
% This is equavalent to the solution (see code):
% solution(flip:flip(0 0 0 0 0) pos:pos(1 2 3 4 5))
%
% Another solution might be:
% 1---0 0---2 2---2 2---0 0---1
%
% This is equavalent to the solution (see code):
% solution(flip:flip(1 1 0 0 0) pos:pos(1 5 2 3 4))
%
NUM = 5
M = matches(
match(0 1)
match(1 0)
match(0 2)
match(2 2)
match(2 0)
)
% Our solver
proc {Solve Root}
% Which numbered match is in each position of the line.
Pos = {MakeTuple pos NUM}
% Whether we rotated the match or not
Flip = {MakeTuple flip NUM}
in
% Post the solution
Root = solution(pos:Pos flip:Flip)
% Initialize the variable domains.
Pos = {FD.tuple pos NUM 1#NUM}
Flip = {FD.tuple flip NUM 0#1}
/* FIXME
{For 1 NUM-1 1 proc {$ I}
% The trailing edge of a placed match is the same the leading
edge
% of the next match.
M.(Pos.I).(2 - Flip.I) =: M.(Pos.(I+1)).(1 + Flip.(I+1))
end}
*/
% We can only place each match once.
{FD.distinct Pos}
{FD.distribute ff Pos}
{FD.distribute ff Flip}
end
{Browser.browse {Search.base.one Solve}}
end
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