Prolog Applying Constraints to Original List Items in Matrix -

i working on project involves matrix. stuck in attempt apply constraints specific elements in matrix. matrix , domain definitions of main class/predicate. so, first 3 predicates creating matrix , defining domains while last 2 predicates labels different variables in regards domain , prints out.

test(solution, n) :-     length(solution,8),     maplist(length_(8), solution), %the variables     maplist(define_domain, solution), %the domains     constraint(solution),     maplist(labeling([]), solution), %labeling variables     maplist(print_row, solution).  length_(length, list) :- length(list, length).  define_domain(x):- x ins 0..9.  ww(x):-     write(x).  print_row(row):-      %nested maplist call works on each element in     maplist(ww, row),     nl. 

so, constraints predicate applies constraint on variables having problems. have facts need capture tried using findall loop through facts , use them determine elements inside list of matrix need apply constraints to. facts contains row, column , length.

the nested findall predicate call uses row determine list inside matrix, column determine index of element of list take , extracting sublist based on index of element , length. outer findall predicate finds position predicates , collects sublists. therefore, have collection of sublists contains elements of matrix constraint needs applied. constraint applied in constraint_apply predicate.

however, discovered findall predicate creates copies of original list instead of using actual elements/variables in original list after struggling many hours. so, constraints being applied affects copies , not originals.

right now, thinking maybe using findall predicate wrongly apply constraints , trying out different ways use it.

i grateful if explain me better way propagate constraints in scenario.any helps/tips appreciated. how apply constraints original list , elements in matrix above?

constraint_apply([]). constraint_apply([x|xs]):-     sum(x, #<, 10),     all_different(x),     constraint_apply(xs).  %extract slice lsit  constraint(xs):-        findall(x, (position(r, c, l), end c+l-1,  findall(y, (nth1(r, xs, n),between(c, end, m), nth1(m, n,y)), x)), row),        constraint_apply(row). 

i had similar problem, , solved using bagof/3 instead of findall/3. cannot test code, here hint needed syntax

constraint(xs):-     bagof(x, r^c^l^end^(         position(r, c, l),         end c+l-1,         bagof(y, n^m^(nth1(r, xs, n), between(c, end, m), nth1(m, n, y)), x)     ), row),     constraint_apply(row).