\\ * * * * * * * * * * * * * * *
\\ coordination sequence library
\\ * * * * * * * * * * * * * * *

width = -1
height = -1
coord = matrix(0,0)
labels = matrix(0,0)

init(screen) = {
	height = #screen;
	width = #screen[1];
	coord = matrix(width, height, x, y, []);
	labels = matrix(width, height, x, y, "");

	for (s=1, #screen,
		my (y=#screen - s);
		my (row = Vec(screen[s]));
		for (x=0, #row-1,
			my (d = row[x+1]);
			if (    (d >= "A" && d <= "Z")
			     || (d >= "a" && d <= "Z")
			     || (d >= "0" && d <= "9"),
				eval(Str("p" d "=" x+I*y));

				labels[1+x, 1+y] = d;
			);
		);
	);
}

up   (z) = z + I*height
down (z) = z - I*height
right(z) = z + width
left (z) = z - width

\\ unidirectional link
link1(z, zz) = {
	my (x=real(z) % width, y=imag(z) % height);
	coord[1+x, 1+y] = concat(coord[1+x, 1+y], zz-z);
}

\\ bidirectional link
link(a, b) = link1(a, b); link1(b, a);

\\ neighbours
neighbours(z) = {
	my (x=real(z) % width, y=imag(z) % height);
	my (n = apply (c -> c + z, coord[1+x, 1+y]));
	\\ print ("#" z " -> " n);
	return (n);
}

compute(z, mx) = {
	my (explored = Set());
	my (current = Set(z));

	for (n=0, mx,
		\\ print ("#" current);
		print (n " " #current);
		if (n==mx, break);
		explored = set union(explored, current);
		my (others = concat(apply(neighbours, current)));
		current = set minus(Set(others), explored);
	);
}

{
	\\ http://rcsr.net/layers/car

	init([
	"..........",
	"A.........",
	"...B...C..",
	"..........",
	"..D.....E.",
	".....F....",
	"..........",
	"..........",
	".....G....",
	"..H.....I.",
	"..........",
	"...J...K..",
	"L.........",
	".........."
	]);

	link(pA, up(pL));
	link(pA, pB);
	link(pA, left(pC));

	link(pB, pC);
	link(pB, pD);

	link(pC, pE);

	link(pD, pF);
	link(pD, left(pE));

	link(pE, pF);

	link(pF, pG);

	link(pG, pH);
	link(pG, pI);

	link(pH, left(pI));
	link(pH, pJ);

	link(pI, pK);

	link(pJ, pL);
	link(pJ, pK);

	link(pK, right(pL));
}

\\ A301285		Coordination sequence for node of type V2 in "car" 2-D tiling (or net).
allocatemem(2^30);
compute(pA, 1000);

quit