indexing
	description: "Stacks with a bounded physical size, implemented by arrays"
	names: dispenser, array
	representation: array
	access: fixed, lifo, membership
	size: fixed
	contents: generic

class interface
	BOUNDED_STACK [G]

create 

	make (n: INTEGER)
			-- Create a stack for at most n items.
		require
			non_negative_argument: n >= 0
		ensure
			stack_allocated: capacity = n;
			empty_stack: count = 0

feature -- Initialization

	make (n: INTEGER)
			-- Create a stack for at most n items.
		require
			non_negative_argument: n >= 0
		ensure
			stack_allocated: capacity = n;
			empty_stack: count = 0
	
feature -- Access

	has (v: G): BOOLEAN
			-- Does v appear in stack?
			-- (Reference or object equality,
			-- based on object_comparison.)
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not empty

	item: G
			-- Last item pushed (i.e. top)
		require -- from ACTIVE
			readable: readable
		require else
			not_empty: count > 0
	
feature -- Measurement

	capacity: INTEGER

	count: INTEGER

	occurrences (v: G): INTEGER
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
	
feature -- Status report

	changeable_comparison_criterion: BOOLEAN
			-- May object_comparison be changed?
			-- (Answer: yes by default.)
			-- (from CONTAINER)

	empty: BOOLEAN
			-- Is structure empty?
			-- (from FINITE)

	extendible: BOOLEAN
		ensure then
			Result = not full

	full: BOOLEAN
			-- Is structure full?
			-- (from BOUNDED)

	object_comparison: BOOLEAN
			-- Must search operations use equal rather than =
			-- for comparing references? (Default: no, use =.)
			-- (from CONTAINER)

	Prunable: BOOLEAN is true

	readable: BOOLEAN
			-- Is there a current item that may be read?
			-- (from DISPENSER)

	Resizable: BOOLEAN is true

	writable: BOOLEAN
			-- Is there a current item that may be modified?
			-- (from DISPENSER)
	
feature -- Status setting

	compare_objects
			-- Ensure that future search operations will use equal
			-- rather than = for comparing references.
			-- (from CONTAINER)
		require -- from CONTAINER
			changeable_comparison_criterion
		ensure -- from CONTAINER
			object_comparison

	compare_references
			-- Ensure that future search operations will use =
			-- rather than equal for comparing references.
			-- (from CONTAINER)
		require -- from CONTAINER
			changeable_comparison_criterion
		ensure -- from CONTAINER
			reference_comparison: not object_comparison
	
feature -- Element change

	append (s: SEQUENCE [G])
			-- Append a copy of s.
			-- (Synonym for fill)
			-- (from DISPENSER)

	extend (v: like item)
			-- Push v on top.
			-- Was declared in BOUNDED_STACK as synonym of extend, force and put.
		require -- from COLLECTION
			extendible: extendible
		ensure -- from COLLECTION
			item_inserted: has (v)
		ensure then -- from BAG
			one_more_occurrence: occurrences (v) = old (occurrences (v)) + 1
		ensure then -- from STACK
			item_pushed: item = v

	fill (other: LINEAR [G])
			-- Fill with as many items of other as possible.
			-- Fill items with greatest index from other first.
			-- Items inserted with lowest index (from other) will
			-- always be on the top of stack.
			-- The representations of other and current structure
			-- need not be the same.
			-- (from STACK)
		require -- from COLLECTION
			other_not_void: other /= void;
			extendible

	force (v: like item)
			-- Push v on top.
			-- Was declared in BOUNDED_STACK as synonym of extend, force and put.
		ensure then -- from STACK
			item_pushed: item = v

	put (v: like item)
			-- Push v on top.
			-- Was declared in BOUNDED_STACK as synonym of extend, force and put.
		require -- from COLLECTION
			extendible: extendible
		ensure -- from COLLECTION
			item_inserted: has (v)
		ensure then -- from STACK
			item_pushed: item = v

	replace (v: like item)
			-- Replace top item by v.
		require -- from ACTIVE
			writable: writable
		ensure -- from ACTIVE
			item_replaced: item = v
	
feature -- Removal

	remove
			-- Remove top item.
		require -- from ACTIVE
			prunable: prunable;
			writable: writable
		require else
			not_empty: count /= 0

	wipe_out
			-- Remove all items.
		require -- from COLLECTION
			prunable
		ensure -- from COLLECTION
			wiped_out: empty
	
feature -- Conversion

	linear_representation: ARRAYED_LIST [G]
			-- Representation as a linear structure
			-- (in the reverse order of original insertion)
	
invariant

		-- from GENERAL
	reflexive_equality: standard_is_equal (Current);
	reflexive_conformance: conforms_to (Current);
	count_small_enough: count <= capacity;
	extendible_definition: extendible = not full;
		-- from DISPENSER
	readable_definition: readable = not empty;
	writable_definition: writable = not empty;
		-- from ACTIVE
	writable_constraint: writable implies readable;
	empty_constraint: empty implies (not readable) and (not writable);
		-- from FINITE
	empty_definition: empty = (count = 0);
	non_negative_count: count >= 0;
		-- from BOUNDED
	valid_count: count <= capacity;
	full_definition: full = (count = capacity);

end -- class BOUNDED_STACK