/tutorial/hanoi/tower.e

  1class TOWER
  2
  3creation {ANY}
  4	full, empty
  5
  6feature {}
  7	t: ARRAY[INTEGER]
  8
  9	top: INTEGER
 10
 11feature {}
 12	full (n: INTEGER) is
 13		require
 14			n >= 1
 15		local
 16			i: INTEGER
 17		do
 18			create t.make(1, n)
 19			from
 20				i := n
 21			until
 22				i = 0
 23			loop
 24				t.put(n - i + 1, i)
 25				i := i - 1
 26			end
 27			top := n
 28		ensure
 29			nb = n
 30			top = nb
 31			t.item(top) = 1
 32		end
 33
 34	empty (n: INTEGER) is
 35		require
 36			n >= 1
 37		do
 38			create t.make(1, n)
 39			top := 1
 40		ensure
 41			nb = n
 42			top = 1
 43		end
 44
 45feature {HANOI}
 46	nb: INTEGER is
 47		do
 48			Result := t.upper
 49		end
 50
 51	show_a_discus (d: INTEGER; picture: STRING) is
 52		require
 53			1 <= d
 54			d <= nb
 55			picture /= Void
 56		local
 57			nb_of_free_slots, nb_of_used_slots, i: INTEGER
 58		do
 59			nb_of_used_slots := t.item(d)
 60			nb_of_free_slots := nb - nb_of_used_slots
 61			from
 62				i := nb_of_free_slots
 63			until
 64				i = 0
 65			loop
 66				picture.extend(' ')
 67				i := i - 1
 68			end
 69			from
 70				i := nb_of_used_slots
 71			until
 72				i = 0
 73			loop
 74				picture.extend('=')
 75				i := i - 1
 76			end
 77			picture.extend('|')
 78			from
 79				i := nb_of_used_slots
 80			until
 81				i = 0
 82			loop
 83				picture.extend('=')
 84				i := i - 1
 85			end
 86			from
 87				i := nb_of_free_slots
 88			until
 89				i = 0
 90			loop
 91				picture.extend(' ')
 92				i := i - 1
 93			end
 94		end
 95
 96	remove_discus: INTEGER is
 97		do
 98			debug
 99				if t.item(top) = 0 then
100					std_error.put_string("Error in 'remove_discus'.%N")
101					crash
102				end
103			end
104			Result := t.item(top)
105			t.put(0, top)
106			if top > 1 then
107				top := top - 1
108			end
109		ensure
110			top >= 1
111		end
112
113	add_discus (d: INTEGER) is
114		do
115			debug
116				if top = nb then
117					std_error.put_string("Error in 'add_discus', %
118                                    %the tower was already full.%N")
119					crash
120				end
121				if d > t.item(top) then
122					--	       std_error.put_string("Error in 'add_discus', the %
123					--				    %discus you wanted to put is larger %
124					--				    %than allowed.");
125					--	       crash;
126				end
127			end
128			if t.item(top) > d then
129				top := top + 1
130				t.put(d, top)
131			end
132			if t.item(top) = 0 then
133				t.put(d, top)
134			end
135		ensure
136			top <= nb
137		end
138
139end -- class TOWER