Prolog Using findall/3 on a Matrix

Question

I have the following matrix in my SWI prolog;

 matrix(1,[  [*,*,*,*,*,*,*,*,*,*,*,*],
        [*,*,*,spots(2,4),spots(2,5),*,*,*,*,spots(2,10),spots(2,11),*],
        [*,*,*,spots(3,4),spots(3,5),spots(3,6),spots(3,7),*,*,spots(3,10),spots(3,11),*],
        [*,*,spots(4,3),spots(4,4),*,spots(4,6),spots(4,7),spots(4,8),spots(4,9),*,spots(4,11),spots(4,12)],
        [*,spots(5,2),spots(5,3),spots(5,4),spots(5,5),*,*,spots(5,8),spots(5,9),*,spots(5,11),spots(5,12)],
        [*,spots(6,2),spots(6,3),*,spots(6,5),spots(6,6),spots(6,7),spots(6,8),*,spots(6,10),spots(6,11),spots(6,12)],
        [*,*,spots(7,3),spots(7,4),*,spots(7,6),spots(7,7),spots(7,8),*,spots(7,10),spots(7,11),*],
        [*,spots(8,2),spots(8,3),spots(8,4),*,spots(8,6),spots(8,7),spots(8,8),spots(8,9),*,spots(8,11),spots(8,12)],
        [*,spots(9,2),spots(9,3),*,spots(9,5),spots(9,6),*,*,spots(9,9),spots(9,10),spots(9,11),spots(9,12)],
        [*,spots(10,2),spots(10,3),*,spots(10,5),spots(10,6),spots(10,7),spots(10,8),*,spots(10,10),spots(10,11),*]
        [*,*,spots(11,3),spots(11,4),*,*,spots(11,7),spots(11,8),spots(11,9),spots(11,10),*,*],
        [*,*,spots(12,3),spots(12,4),*,*,*,*,spots(12,9),spots(12,10),*,*]]).

I want to use a findall/3 predicate so that I can get a list of all the spot(X,Y) facts like >>>

 findall(spots(X,Y),matrix(1,Map),X). 

Which should return something like the following;

 X = (spots(2,4), spots(2,5), spots(2,10), spots(2,11), spots(3,4) etc .... spots(12,10)). 

However, I'm very confused in how to implement this, due to the matrix being composed of a list within a list. Would appreciate if someone could show me a configured predicate in order to achieve a list like stated.

Thanks for any help!!! - really appreciate it!

Edit - may be able to use this code found below and unable to see how I could implement this into a second findall/3 statement. Really stuck so appreciate any help on this.

at(Mat, Row, Col, Val) :- nth1(Row, Mat, ARow), nth1(Col, ARow, Val).

Answer 1

Just think what your predicate should describe: You want to find all terms of the form spots(_,_) in a list of lists that otherwise consists of atoms *.

:- use_module(library(lists)).

matrix_spots([],[]).                % no spots in the empty matrix
matrix_spots([R|Rs],S) :-
    row_spots(R,RSs),               % RSs ... spots in row R
    matrix_spots(Rs,S1),            % S1 ... spots in the remaining rows
    append(RSs,S1,S).               % S ... RSs followed by S1

row_spots([],[]).                   % no spots in an empty row
row_spots([E|Es],[E|RSs]) :-        % E is in the list of spots
    E=spots(_,_),                   % if it is a spot
    row_spots(Es,RSs).              % RSs ... spots in rest of row
row_spots([*|Es],RSs) :-            % * is not in the list of spots
    row_spots(Es,RSs).              % Rss ... spots in rest of row

Now you can query your matrix for all its spots:

   ?- matrix(1,M), matrix_spots(M,S).
M = [[*,*,*,*,*,*,*,*,*,*,*,*],[*,*,*,spots(2,4),spots(2,5),*,*,*,*,spots(2,10),spots(2,11),*],[*,*,*,spots(3,4),spots(3,5),spots(3,6),spots(3,7),*,*,spots(3,10),spots(3,11),*],[*,*,spots(4,3),spots(4,4),*,spots(4,6),spots(4,7),spots(4,8),spots(4,9),*,spots(4,11),spots(4,12)],[*,spots(5,2),spots(5,3),spots(5,4),spots(5,5),*,*,spots(5,8),spots(5,9),*,spots(5,11),spots(5,12)],[*,spots(6,2),spots(6,3),*,spots(6,5),spots(6,6),spots(6,7),spots(6,8),*,spots(6,10),spots(6,11),spots(6,12)],[*,*,spots(7,3),spots(7,4),*,spots(7,6),spots(7,7),spots(7,8),*,spots(7,10),spots(7,11),*],[*,spots(8,2),spots(8,3),spots(8,4),*,spots(8,6),spots(8,7),spots(8,8),spots(8,9),*,spots(8,11),spots(8,12)],[*,spots(9,2),spots(9,3),*,spots(9,5),spots(9,6),*,*,spots(9,9),spots(9,10),spots(9,11),spots(9,12)],[*,spots(10,2),spots(10,3),*,spots(10,5),spots(10,6),spots(10,7),spots(10,8),*,spots(10,10),spots(10,11),*],[*,*,spots(11,3),spots(11,4),*,*,spots(11,7),spots(11,8),spots(11,9),spots(11,10),*,*],[*,*,spots(12,3),spots(12,4),*,*,*,*,spots(12,9),spots(12,10),*,*]],
S = [spots(2,4),spots(2,5),spots(2,10),spots(2,11),spots(3,4),spots(3,5),spots(3,6),spots(3,7),spots(3,10),spots(3,11),spots(4,3),spots(4,4),spots(4,6),spots(4,7),spots(4,8),spots(4,9),spots(4,11),spots(4,12),spots(5,2),spots(5,3),spots(5,4),spots(5,5),spots(5,8),spots(5,9),spots(5,11),spots(5,12),spots(6,2),spots(6,3),spots(6,5),spots(6,6),spots(6,7),spots(6,8),spots(6,10),spots(6,11),spots(6,12),spots(7,3),spots(7,4),spots(7,6),spots(7,7),spots(7,8),spots(7,10),spots(7,11),spots(8,2),spots(8,3),spots(8,4),spots(8,6),spots(8,7),spots(8,8),spots(8,9),spots(8,11),spots(8,12),spots(9,2),spots(9,3),spots(9,5),spots(9,6),spots(9,9),spots(9,10),spots(9,11),spots(9,12),spots(10,2),spots(10,3),spots(10,5),spots(10,6),spots(10,7),spots(10,8),spots(10,10),spots(10,11),spots(11,3),spots(11,4),spots(11,7),spots(11,8),spots(11,9),spots(1ts(12,4),spots(12,9),spots(12,10)] ? ;
no

Note that you have a typo in your example matrix: at the end of the 10th list the comma is missing: ...spots(10,11),*],

Edit:

Here is a dcg version as suggested by @mat in the comments. It is indeed much easier readable:

matrix_spots(M,S) :-
    phrase(rows(M),S).

rows([]) -->                % no spots in the empty matrix
    [].
rows([R|Rs]) -->
    row(R),                 % all spots in row R
    rows(Rs).               % all spots in the remaining rows

row([]) -->                 % no spots in an empty row
    [].
row([*|Xs]) -->             % no spot at this position in the row
    row(Xs).                % but there might be in the remainder 
row([spots(A,B)|Xs]) -->    % spot at this position
    [spots(A,B)],           % is in the list
    row(Xs).                % and the spots in the rest of the row

The query above can be used one-to-one with this dcg-version.

Concerning your (@User15388472) findall/3 question in the comments: Imagine you had a predicate matrix_spot/2 that is matching one term of the form spots(A,B) as second argument instead of a list of all spots. That predicate could look something like that:

matrix_spot([R|Rs],S) :-
    row_spot(R,S).                      % S is in row R
matrix_spot([R|Rs],S) :-                % S is not in R but
    matrix_spot(Rs,S).                  % in one of the other rows Rs

row_spot([spots(A,B)|Xs],spots(A,B)).   % head of the list is the spot
row_spot([X|Xs],S) :-
    row_spot(Xs,S).                     % S is in the tail of the list

If you query this predicate you get one spots(A,B) at a time as an answer:

   ?- matrix(1,M), matrix_spot(M,S).
M = [[*,*,*,*,*,*,*,*,*,*,*,*],[*,*,*,spots(2,4),spots(2,5),*,*,*,*,spots(2,10),spots(2,11),*],[*,*,*,spots(3,4),spots(3,5),spots(3,6),spots(3,7),*,*,spots(3,10),spots(3,11),*],[*,*,spots(4,3),spots(4,4),*,spots(4,6),spots(4,7),spots(4,8),spots(4,9),*,spots(4,11),spots(4,12)],[*,spots(5,2),spots(5,3),spots(5,4),spots(5,5),*,*,spots(5,8),spots(5,9),*,spots(5,11),spots(5,12)],[*,spots(6,2),spots(6,3),*,spots(6,5),spots(6,6),spots(6,7),spots(6,8),*,spots(6,10),spots(6,11),spots(6,12)],[*,*,spots(7,3),spots(7,4),*,spots(7,6),spots(7,7),spots(7,8),*,spots(7,10),spots(7,11),*],[*,spots(8,2),spots(8,3),spots(8,4),*,spots(8,6),spots(8,7),spots(8,8),spots(8,9),*,spots(8,11),spots(8,12)],[*,spots(9,2),spots(9,3),*,spots(9,5),spots(9,6),*,*,spots(9,9),spots(9,10),spots(9,11),spots(9,12)],[*,spots(10,2),spots(10,3),*,spots(10,5),spots(10,6),spots(10,7),spots(10,8),*,spots(10,10),spots(10,11),*],[*,*,spots(11,3),spots(11,4),*,*,spots(11,7),spots(11,8),spots(11,9),spots(11,10),*,*],[*,*,spots(12,3),spots(12,4),*,*,*,*,spots(12,9),spots(12,10),*,*]],
S = spots(2,4) ? ;
M = [[*,*,*,*,*,*,*,*,*,*,*,*],[*,*,*,spots(2,4),spots(2,5),*,*,*,*,spots(2,10),spots(2,11),*],[*,*,*,spots(3,4),spots(3,5),spots(3,6),spots(3,7),*,*,spots(3,10),spots(3,11),*],[*,*,spots(4,3),spots(4,4),*,spots(4,6),spots(4,7),spots(4,8),spots(4,9),*,spots(4,11),spots(4,12)],[*,spots(5,2),spots(5,3),spots(5,4),spots(5,5),*,*,spots(5,8),spots(5,9),*,spots(5,11),spots(5,12)],[*,spots(6,2),spots(6,3),*,spots(6,5),spots(6,6),spots(6,7),spots(6,8),*,spots(6,10),spots(6,11),spots(6,12)],[*,*,spots(7,3),spots(7,4),*,spots(7,6),spots(7,7),spots(7,8),*,spots(7,10),spots(7,11),*],[*,spots(8,2),spots(8,3),spots(8,4),*,spots(8,6),spots(8,7),spots(8,8),spots(8,9),*,spots(8,11),spots(8,12)],[*,spots(9,2),spots(9,3),*,spots(9,5),spots(9,6),*,*,spots(9,9),spots(9,10),spots(9,11),spots(9,12)],[*,spots(10,2),spots(10,3),*,spots(10,5),spots(10,6),spots(10,7),spots(10,8),*,spots(10,10),spots(10,11),*],[*,*,spots(11,3),spots(11,4),*,*,spots(11,7),spots(11,8),spots(11,9),spots(11,10),*,*],[*,*,spots(12,3),spots(12,4),*,*,*,*,spots(12,9),spots(12,10),*,*]],
S = spots(2,5) ? ;
...

In a scenario like this you can use findall/3 to find all terms spots(A,B) in the matrix:

   ?- matrix(1,M), findall(S,matrix_spot(M,S),Spots).
M = [[*,*,*,*,*,*,*,*,*,*,*,*],[*,*,*,spots(2,4),spots(2,5),*,*,*,*,spots(2,10),spots(2,11),*],[*,*,*,spots(3,4),spots(3,5),spots(3,6),spots(3,7),*,*,spots(3,10),spots(3,11),*],[*,*,spots(4,3),spots(4,4),*,spots(4,6),spots(4,7),spots(4,8),spots(4,9),*,spots(4,11),spots(4,12)],[*,spots(5,2),spots(5,3),spots(5,4),spots(5,5),*,*,spots(5,8),spots(5,9),*,spots(5,11),spots(5,12)],[*,spots(6,2),spots(6,3),*,spots(6,5),spots(6,6),spots(6,7),spots(6,8),*,spots(6,10),spots(6,11),spots(6,12)],[*,*,spots(7,3),spots(7,4),*,spots(7,6),spots(7,7),spots(7,8),*,spots(7,10),spots(7,11),*],[*,spots(8,2),spots(8,3),spots(8,4),*,spots(8,6),spots(8,7),spots(8,8),spots(8,9),*,spots(8,11),spots(8,12)],[*,spots(9,2),spots(9,3),*,spots(9,5),spots(9,6),*,*,spots(9,9),spots(9,10),spots(9,11),spots(9,12)],[*,spots(10,2),spots(10,3),*,spots(10,5),spots(10,6),spots(10,7),spots(10,8),*,spots(10,10),spots(10,11),*],[*,*,spots(11,3),spots(11,4),*,*,spots(11,7),spots(11,8),spots(11,9),spots(11,10),*,*],[*,*,spots(12,3),spots(12,4),*,*,*,*,spots(12,9),spots(12,10),*,*]],
Spots = [spots(2,4),spots(2,5),spots(2,10),spots(2,11),spots(3,4),spots(3,5),spots(3,6),spots(3,7),spots(3,10),spots(3,11),spots(4,3),spots(4,4),spots(4,6),spots(4,7),spots(4,8),spots(4,9),spots(4,11),spots(4,12),spots(5,2),spots(5,3),spots(5,4),spots(5,5),spots(5,8),spots(5,9),spots(5,11),spots(5,12),spots(6,2),spots(6,3),spots(6,5),spots(6,6),spots(6,7),spots(6,8),spots(6,10),spots(6,11),spots(6,12),spots(7,3),spots(7,4),spots(7,6),spots(7,7),spots(7,8),spots(7,10),spots(7,11),spots(8,2),spots(8,3),spots(8,4),spots(8,6),spots(8,7),spots(8,8),spots(8,9),spots(8,11),spots(8,12),spots(9,2),spots(9,3),spots(9,5),spots(9,6),spots(9,9),spots(9,10),spots(9,11),spots(9,12),spots(10,2),spots(10,3),spots(10,5),spots(10,6),spots(10,7),spots(10,8),spots(10,10),spots(10,11),spots(11,3),spots(11,4),spots(11,7),spots(11,8),spots(11,9),spots(11,10),spots(12,3),spots(12,4),spots(12,9),spots(12,10)]