class TOWER

creation {ANY}
	full, empty

feature {}
	t: ARRAY[INTEGER]

	top: INTEGER

feature {}
	full (n: INTEGER) is
		require
			n >= 1
		local
			i: INTEGER
		do
			create t.make(1, n)
			from
				i := n
			until
				i = 0
			loop
				t.put(n - i + 1, i)
				i := i - 1
			end
			top := n
		ensure
			nb = n
			top = nb
			t.item(top) = 1
		end

	empty (n: INTEGER) is
		require
			n >= 1
		do
			create t.make(1, n)
			top := 1
		ensure
			nb = n
			top = 1
		end

feature {HANOI}
	nb: INTEGER is
		do
			Result := t.upper
		end

	show_a_discus (d: INTEGER; picture: STRING) is
		require
			1 <= d
			d <= nb
			picture /= Void
		local
			nb_of_free_slots, nb_of_used_slots, i: INTEGER
		do
			nb_of_used_slots := t.item(d)
			nb_of_free_slots := nb - nb_of_used_slots
			from
				i := nb_of_free_slots
			until
				i = 0
			loop
				picture.extend(' ')
				i := i - 1
			end
			from
				i := nb_of_used_slots
			until
				i = 0
			loop
				picture.extend('=')
				i := i - 1
			end
			picture.extend('|')
			from
				i := nb_of_used_slots
			until
				i = 0
			loop
				picture.extend('=')
				i := i - 1
			end
			from
				i := nb_of_free_slots
			until
				i = 0
			loop
				picture.extend(' ')
				i := i - 1
			end
		end

	remove_discus: INTEGER is
		do
			debug
				if t.item(top) = 0 then
					std_error.put_string("Error in 'remove_discus'.%N")
					crash
				end
			end
			Result := t.item(top)
			t.put(0, top)
			if top > 1 then
				top := top - 1
			end
		ensure
			top >= 1
		end

	add_discus (d: INTEGER) is
		do
			debug
				if top = nb then
					std_error.put_string("Error in 'add_discus', %
                                    %the tower was already full.%N")
					crash
				end
				if d > t.item(top) then
					--	       std_error.put_string("Error in 'add_discus', the %
					--				    %discus you wanted to put is larger %
					--				    %than allowed.");
					--	       crash;
				end
			end
			if t.item(top) > d then
				top := top + 1
				t.put(d, top)
			end
			if t.item(top) = 0 then
				t.put(d, top)
			end
		ensure
			top <= nb
		end

end -- class TOWER