cake(N) :-
	phrase(cake(N), L),
	string_to_list(S, L),
	write(S).

cake(N0) -->
	{ N is N0 - 1 },
	tok_spacer_width("/\\", " ", N), "\n",
	tok_spacer_width("\\/", " ", N), "\n",
	{ Ncan is N * 2 },
	candle(Ncan, N),
	tok_spacer_width("oo", "o", N), "\n",
	body(N0, N0),
	tok_spacer_width("oo", "o", N), "\n".

candle(0, _) --> [].
candle(N, M) -->
	tok_spacer_width("||", " ", M), "\n",
	{ N1 is N - 1 },
	candle(N1, M).

body(1, _) --> [].
body(N, M) -->
	{ N > 1 },
	{ N1 is N - 1 },
	ubody(N, M), "\n",
	body(N1, M),
	lbody(N, M), "\n".

ubody(N, M) -->
	{ N1 is N - 1 },
	{ phrase(utok(N, M), Tok) },
	tok_spacer_width(Tok, "o", N1).

lbody(N, M) -->
	{ N1 is N - 1 },
	{ phrase(ltok(N, M), Tok) },
	tok_spacer_width(Tok, "o", N1).

utok(N, M) -->
	{ DN is M - N },
	"/",
	repeat("xx", DN),
	"\\".

ltok(N, M) -->
	{ DN is M - N },
	"\\",
	repeat("xx", DN),
	"/".

tok_spacer_width(C, S, N) -->
	{ N2 is N * 2 },
	repeat(S, N),
	C,
	repeat(S, N2),
	C,
	repeat(S, N2),
	C,
	repeat(S, N2),
	C,
	repeat(S, N2),
	C,
	repeat(S, N).

repeat(_, 0) --> [].
repeat(C, N) -->
	{ N > 0 },
	C,
	{ N1 is N - 1 },
	repeat(C, N1).