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Langton's ant: Difference between revisions
→{{header|Processing}}
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set(x,y,white?#ffffff:#000000);
}</lang>
=={{header|Prolog}}==
This sort of problem, when stated in Prolog, reads a bit like a story book. Our main goal (go) succeeds if we can move north from the middle of the 100x100 matrix, and update_win- which outputs the black/1 blocks. The move/3 and direction/3 goals are really self explanatory.
<lang prolog>%_______________________________________________________________
% Langtons ant.
:-dynamic
black/1.
plot_point(Row, Col) :- % Output a 5x5 black box at R,C
new(C, box(5,5)), X is Col * 5 - 2, Y is Row * 5 - 2,
send(C, colour, colour(black)), send(C, fill_pattern, colour(blue)),
send(C, center(point(X,Y))), send(@win, display, C).
update_win :- % Make a 500x500 window, find all the black points and plot them
new(@win, window('Langdons\' Ant')),
send(@win, size, size(500,500)), send(@win, open),
black(Row/Col),plot_point(Row,Col),fail.
update_win.
direction(Row, Col, left) :- black(Row/Col), !, retract(black(Row/Col)).
direction(Row, Col, right):- not(black(Row/Col)), !, assert(black(Row/Col)).
move(_, Row,Col) :- (Row < 0; Col < 0; Row > 99; Col > 99), !.
move(north,Row,Col) :-
(direction(Row,Col,left), C is Col - 1, !, move(west, Row, C));
(direction(Row,Col,right), C is Col + 1, !, move(east, Row, C)).
move(south,Row,Col) :-
(direction(Row,Col,right), C is Col - 1, !, move(west, Row, C));
(direction(Row,Col,left), C is Col + 1, !, move(east, Row, C)).
move(east,Row,Col) :-
(direction(Row,Col,right), R is Row + 1, !, move(south, R, Col));
(direction(Row,Col,left), R is Row - 1, !, move(north, R, Col)).
move(west,Row,Col) :-
(direction(Row,Col,left), R is Row + 1, !, move(south, R, Col));
(direction(Row,Col,right), R is Row - 1, !, move(north, R, Col)).
go :- retractall(black(_)), move(north,49,49), update_win.</lang>
=={{header|PureBasic}}==
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