note
	description: "Priority queues implemented as heaps"
	library: "Free implementation of ELKS library"
	legal: "See notice at end of class."
	status: "See notice at end of class."
	names: sorted_priority_queue, dispenser, heap
	representation: heap
	access: fixed, membership
	contents: generic
	date: "$Date: 2018-12-15 18:06:16 +0000 (Sat, 15 Dec 2018) $"
	revision: "$Revision: 102608 $"

class 
	HEAP_PRIORITY_QUEUE [G -> COMPARABLE]

create 
	make,
	make_from_iterable

feature {NONE} -- Initialization

	default_create
			-- Process instances of classes with no creation clause.
			-- (Default: do nothing.)
			-- (from ANY)
		do
		end

	make (n: INTEGER_32)
			-- Allocate heap space.
		do
			create area.make_empty (n)
		end

	make_from_iterable (other: ITERABLE [G])
			-- Create a priority queue with all items obtained from other.
		do
			make (estimated_count_of (other))
			across
				other as o
			loop
				extend (o.item)
			end
		end
	
feature -- Access

	generating_type: TYPE [detachable HEAP_PRIORITY_QUEUE [G]]
			-- Type of current object
			-- (type of which it is a direct instance)
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			generating_type_not_void: Result /= Void
		end

	generator: STRING_8
			-- Name of current object's generating class
			-- (base class of the type of which it is a direct instance)
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			generator_not_void: Result /= Void
			generator_not_empty: not Result.is_empty
		end

	has (v: G): BOOLEAN
			-- Does structure include v?
			-- (Reference or object equality,
			-- based on object_comparison.)
		local
			i, nb: INTEGER_32
			l_area: like area
		do
			l_area := area
			nb := l_area.count
			if object_comparison and v /= Void then
				from
				until
					i = nb or Result
				loop
					Result := l_area.item (i) ~ v
					i := i + 1
				end
			else
				from
				until
					i = nb or Result
				loop
					Result := l_area.item (i) = v
					i := i + 1
				end
			end
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty
		end

	item: G
			-- Entry at top of heap.
		require -- from ACTIVE
			readable: readable
		do
			Result := i_th (1)
		end
	
feature {HEAP_PRIORITY_QUEUE, HEAP_PRIORITY_QUEUE_ITERATION_CURSOR} -- Access

	area: SPECIAL [G]
			-- Storage for queue.

	Lower: INTEGER_32 = 1
			-- Lower bound for internal access to area.
	
feature -- Measurement

	additional_space: INTEGER_32
			-- Proposed number of additional items
			-- (from RESIZABLE)
		do
			Result := (capacity // 2).max (Minimal_increase)
		ensure -- from RESIZABLE
			at_least_one: Result >= 1
		end

	capacity: INTEGER_32
			-- Number of items that may be stored
		do
			Result := area.capacity
		ensure -- from BOUNDED
			capacity_non_negative: Result >= 0
		end

	count: INTEGER_32
			-- Number of items
		do
			Result := area.count
		ensure -- from FINITE
			count_non_negative: Result >= 0
		end

	Growth_percentage: INTEGER_32 = 50
			-- Percentage by which structure will grow automatically
			-- (from RESIZABLE)

	index_set: INTEGER_INTERVAL
			-- Range of acceptable indexes
		do
			create Result.make (1, count)
		ensure then
			count_definition: Result.count = count
		end

	Minimal_increase: INTEGER_32 = 5
			-- Minimal number of additional items
			-- (from RESIZABLE)

	occurrences (v: G): INTEGER_32
			-- Number of times v appears in structure
			-- (Reference or object equality,
			-- based on object_comparison.)
		local
			i, nb: INTEGER_32
		do
			if object_comparison then
				from
					i := Lower
					nb := count
				until
					i > nb
				loop
					if i_th (i) ~ v then
						Result := Result + 1
					end
					i := i + 1
				end
			else
				from
					i := Lower
					nb := count
				until
					i > nb
				loop
					if i_th (i) = v then
						Result := Result + 1
					end
					i := i + 1
				end
			end
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
		end
	
feature {NONE} -- Measurement

	estimated_count_of (other: ITERABLE [G]): INTEGER_32
			-- Estimated number of elements in other.
			-- (from CONTAINER)
		do
			if attached {FINITE [G]} other as f then
				Result := f.count
			elseif attached {READABLE_INDEXABLE [G]} other as r then
				Result := r.upper - r.lower + 1
			end
		ensure -- from CONTAINER
			instance_free: class
			non_negative_result: Result >= 0
		end
	
feature -- Comparison

	frozen deep_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void
			-- or attached to isomorphic object structures?
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.is_deep_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			shallow_implies_deep: standard_equal (a, b) implies Result
			both_or_none_void: (a = Void) implies (Result = (b = Void))
			same_type: (Result and (a /= Void)) implies (b /= Void and then a.same_type (b))
			symmetric: Result implies deep_equal (b, a)
		end

	frozen equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void or attached
			-- to objects considered equal?
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.is_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.is_equal (b))
		end

	frozen is_deep_equal alias "≡≡≡" (other: HEAP_PRIORITY_QUEUE [G]): BOOLEAN
			-- Are Current and other attached to isomorphic object structures?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		ensure -- from ANY
			shallow_implies_deep: standard_is_equal (other) implies Result
			same_type: Result implies same_type (other)
			symmetric: Result implies other.is_deep_equal (Current)
		end

	is_equal (other: like Current): BOOLEAN
			-- Is other attached to an object considered
			-- equal to current object?
		require -- from ANY
			other_not_void: other /= Void
		local
			l_current, l_other: like Current
		do
			if other = Current then
				Result := True
			elseif object_comparison = other.object_comparison and then count = other.count then
				l_current := twin
				l_other := other.twin
				from
					Result := True
				until
					not Result or l_current.is_empty
				loop
					if object_comparison then
						Result := l_current.item ~ l_other.item
					else
						Result := l_current.item = l_other.item
					end;
					l_current.remove;
					l_other.remove
				end
			end
		ensure -- from ANY
			symmetric: Result implies other ~ Current
			consistent: standard_is_equal (other) implies Result
		end

	frozen standard_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void or attached to
			-- field-by-field identical objects of the same type?
			-- Always uses default object comparison criterion.
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.standard_is_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.standard_is_equal (b))
		end

	frozen standard_is_equal alias "≜" (other: HEAP_PRIORITY_QUEUE [G]): BOOLEAN
			-- Is other attached to an object of the same type
			-- as current object, and field-by-field identical to it?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		ensure -- from ANY
			same_type: Result implies same_type (other)
			symmetric: Result implies other.standard_is_equal (Current)
		end
	
feature {NONE} -- Comparison

	safe_less_than (a, b: G): BOOLEAN
			-- Same as a < b when a and b are not Void.
			-- If a is Void and b is not, then True
			-- Otherwise False
		do
			if a /= Void and b /= Void then
				Result := a < b
			elseif a = Void and b /= Void then
				Result := True
			else
				Result := False
			end
		ensure
			asymmetric: Result implies not safe_less_than (b, a)
		end
	
feature -- Status report

	changeable_comparison_criterion: BOOLEAN
			-- May object_comparison be changed?
			-- (Answer: yes by default.)
			-- (from CONTAINER)
		do
			Result := True
		end

	conforms_to (other: ANY): BOOLEAN
			-- Does type of current object conform to type
			-- of other (as per Eiffel: The Language, chapter 13)?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		end

	empty: BOOLEAN
		obsolete "ELKS 2000: Use `is_empty' instead. [2017-05-31]"
			-- Is there no element?
			-- (from CONTAINER)
		do
			Result := is_empty
		end

	extendible: BOOLEAN
			-- May items be added?
		do
			Result := not full
		end

	full: BOOLEAN
			-- Is structure full?
			-- (from BOUNDED)
		require -- from  BOX
			True
		do
			Result := count = capacity
		end

	is_empty: BOOLEAN
			-- Is structure empty?
			-- (from FINITE)
		require -- from  CONTAINER
			True
		do
			Result := count = 0
		end

	is_inserted (v: G): BOOLEAN
			-- Has v been inserted by the most recent insertion?
			-- (By default, the value returned is equivalent to calling 
			-- has (v). However, descendants might be able to provide more
			-- efficient implementations.)
			-- (from COLLECTION)
		do
			Result := has (v)
		end

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

	Prunable: BOOLEAN = True
			-- May items be removed? (Answer: yes.)

	readable: BOOLEAN
			-- Is there a current item that may be read?
			-- (from DISPENSER)
		do
			Result := not is_empty
		end

	replaceable: BOOLEAN
			-- Can current item be replaced?
		do
			Result := False
		end

	resizable: BOOLEAN
			-- May capacity be changed? (Answer: yes.)
			-- (from RESIZABLE)
		do
			Result := True
		end

	same_type (other: ANY): BOOLEAN
			-- Is type of current object identical to type of other?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		ensure -- from ANY
			definition: Result = (conforms_to (other) and other.conforms_to (Current))
		end

	writable: BOOLEAN
			-- Is there a current item that may be modified?
			-- (from DISPENSER)
		do
			Result := not is_empty
		end
	
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: changeable_comparison_criterion
		do
			object_comparison := True
		ensure -- from CONTAINER
				object_comparison
		end

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

	append (s: SEQUENCE [G])
			-- Append a copy of s.
			-- (Synonym for fill)
			-- (from DISPENSER)
		require -- from DISPENSER
			s_not_void: s /= Void
			extendible: extendible
		do
			fill (s)
		end

	extend (v: like item)
			-- Add item v.
		require -- from COLLECTION
			extendible: extendible
		do
			put (v)
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		end

	fill (other: CONTAINER [G])
			-- Fill with as many items of other as possible.
			-- The representations of other and current structure
			-- need not be the same.
			-- (from COLLECTION)
		require -- from COLLECTION
			other_not_void: other /= Void
			extendible: extendible
		local
			lin_rep: LINEAR [G]
		do
			lin_rep := other.linear_representation
			from
				lin_rep.start
			until
				not extendible or else lin_rep.off
			loop
				extend (lin_rep.item);
				lin_rep.forth
			end
		end

	force (v: like item)
			-- Add item v at its proper position.
		require -- from DISPENSER
			extendible: extendible
		do
			if full then
				grow (count + additional_space)
			end
			put (v)
		ensure -- from DISPENSER
			item_inserted: is_inserted (v)
		end

	put (v: like item)
			-- Insert item v at its proper position.
		require -- from COLLECTION
			extendible: extendible
		local
			i: INTEGER_32
		do
			from
				i := count + 1
			until
				i <= 1 or else not safe_less_than (i_th (i // 2), v)
			loop
				force_i_th (i_th (i // 2), i)
				i := i // 2
			end
			force_i_th (v, i)
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		end
	
feature -- Removal

	prune (v: G)
			-- Remove first occurrence of v if any.
		require -- from COLLECTION
			prunable: Prunable
		local
			i, nb: INTEGER_32
			l_tmp: ARRAYED_LIST [G]
			l_item: G
			l_done: BOOLEAN
		do
			create l_tmp.make (count)
			if object_comparison then
				from
					i := 1
					nb := count
				until
					i > nb
				loop
					l_item := i_th (i)
					if not l_done and l_item ~ v then
						l_done := True
					else
						l_tmp.extend (l_item)
					end
					i := i + 1
				end
			else
				from
					i := 1
					nb := count
				until
					i > nb
				loop
					l_item := i_th (i)
					if not l_done and l_item = v then
						l_done := True
					else
						l_tmp.extend (l_item)
					end
					i := i + 1
				end
			end
			if l_tmp.count = count - 1 then
				across
					l_tmp as x
				from
					wipe_out
				loop
					put (x.item)
				end
			end
		end

	prune_all (v: G)
			-- Remove all occurrences of v.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from COLLECTION)
		require -- from COLLECTION
			prunable: Prunable
		do
			from
			until
				not has (v)
			loop
				prune (v)
			end
		ensure -- from COLLECTION
			no_more_occurrences: not has (v)
		end

	remove
			-- Remove item of highest value.
		require -- from ACTIVE
			prunable: Prunable
			writable: writable
		local
			i, j: INTEGER_32
			up: like item
			nb: INTEGER_32
			stop: BOOLEAN
		do
			nb := count - 1
			if nb > 0 then
				from
					i := 1
					up := i_th (nb + 1)
				until
					stop or i > nb // 2
				loop
					j := 2 * i
					if (j < nb) and safe_less_than (i_th (j), i_th (j + 1)) then
						j := j + 1
					end
					stop := not safe_less_than (up, i_th (j))
					if not stop then
						put_i_th (i_th (j), i)
						i := j
					end
				end
				put_i_th (up, i)
			end;
			area.remove_tail (1)
		end

	wipe_out
			-- Remove all items.
		require -- from COLLECTION
			prunable: Prunable
		do
			area.wipe_out
		ensure -- from COLLECTION
			wiped_out: is_empty
		end
	
feature -- Resizing

	automatic_grow
			-- Change the capacity to accommodate at least
			-- Growth_percentage more items.
			-- (from RESIZABLE)
		require -- from RESIZABLE
			resizable: resizable
		do
			grow (capacity + additional_space)
		ensure -- from RESIZABLE
			increased_capacity: capacity >= old capacity + old additional_space
		end

	grow (i: INTEGER_32)
			-- Ensure that capacity is at least i.
		require -- from RESIZABLE
			resizable: resizable
		do
			if i > area.capacity then
				area := area.aliased_resized_area (i)
			end
		ensure -- from RESIZABLE
			new_capacity: capacity >= i
		end

	trim
			-- Decrease capacity to the minimum value.
			-- Apply to reduce allocated storage.
		require -- from  RESIZABLE
			True
		local
			n: like count
		do
			n := count
			if n < capacity then
				area := area.aliased_resized_area (n)
			end
		ensure -- from RESIZABLE
			same_count: count = old count
			minimal_capacity: capacity = count
		ensure then
			same_items: linear_representation.is_equal (old linear_representation)
		end
	
feature -- Conversion

	linear_representation: ARRAYED_LIST [G]
			-- Representation as a linear structure
			-- (Sorted according to decreasing priority)
		local
			l_current: like Current
		do
			from
				l_current := twin
				create Result.make (count)
			until
				l_current.is_empty
			loop
				Result.extend (l_current.item);
				l_current.remove
			end
		end
	
feature -- Duplication

	frozen clone (other: detachable ANY): like other
		obsolete "Use `twin' instead. [2017-05-31]"
			-- Void if other is void; otherwise new object
			-- equal to other
			--
			-- For non-void other, clone calls copy;
			-- to change copying/cloning semantics, redefine copy.
			-- (from ANY)
		do
			if other /= Void then
				Result := other.twin
			end
		ensure -- from ANY
			instance_free: class
			equal: Result ~ other
		end

	copy (other: like Current)
			-- Update current object using fields of object attached
			-- to other, so as to yield equal objects.
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		do
			if other /= Current then
				standard_copy (other)
				area := area.twin
			end
		ensure -- from ANY
			is_equal: Current ~ other
		end

	frozen deep_clone (other: detachable ANY): like other
		obsolete "Use `deep_twin' instead. [2017-05-31]"
			-- Void if other is void: otherwise, new object structure
			-- recursively duplicated from the one attached to other
			-- (from ANY)
		do
			if other /= Void then
				Result := other.deep_twin
			end
		ensure -- from ANY
			instance_free: class
			deep_equal: deep_equal (other, Result)
		end

	frozen deep_copy (other: HEAP_PRIORITY_QUEUE [G])
			-- Effect equivalent to that of:
			--		copy (other . deep_twin)
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		do
			copy (other.deep_twin)
		ensure -- from ANY
			deep_equal: deep_equal (Current, other)
		end

	frozen deep_twin: HEAP_PRIORITY_QUEUE [G]
			-- New object structure recursively duplicated from Current.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			deep_twin_not_void: Result /= Void
			deep_equal: deep_equal (Current, Result)
		end

	duplicate (n: INTEGER_32): like Current
		obsolete "[
			Create a new container explicitly using `make_from_iterable` if available.
			Otherwise, replace a call to the feature with code that creates and initializes container.
			[2018-11-30]
		]"
			-- New priority queue containing n greatest items of Current.
		require
			n_positive: n >= 0
			n_in_bounds: n <= count
		local
			l_current: like Current
			l_tmp: ARRAYED_LIST [G]
			i: INTEGER_32
		do
			from
				l_current := twin
				create l_tmp.make (n)
				i := 1
			until
				i > n
			loop
				l_tmp.extend (l_current.item);
				l_current.remove
				i := i + 1
			end
			across
				l_tmp as x
			from
				create Result.make (n)
			loop
				Result.put (x.item)
			end
		end

	frozen standard_clone (other: detachable ANY): like other
		obsolete "Use `standard_twin' instead. [2017-05-31]"
			-- Void if other is void; otherwise new object
			-- field-by-field identical to other.
			-- Always uses default copying semantics.
			-- (from ANY)
		do
			if other /= Void then
				Result := other.standard_twin
			end
		ensure -- from ANY
			instance_free: class
			equal: standard_equal (Result, other)
		end

	frozen standard_copy (other: HEAP_PRIORITY_QUEUE [G])
			-- Copy every field of other onto corresponding field
			-- of current object.
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		external
			"built_in"
		ensure -- from ANY
			is_standard_equal: standard_is_equal (other)
		end

	frozen standard_twin: HEAP_PRIORITY_QUEUE [G]
			-- New object field-by-field identical to other.
			-- Always uses default copying semantics.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			standard_twin_not_void: Result /= Void
			equal: standard_equal (Result, Current)
		end

	frozen twin: HEAP_PRIORITY_QUEUE [G]
			-- New object equal to Current
			-- twin calls copy; to change copying/twinning semantics, redefine copy.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			twin_not_void: Result /= Void
			is_equal: Result ~ Current
		end
	
feature -- Basic operations

	frozen as_attached: attached HEAP_PRIORITY_QUEUE [G]
		obsolete "Remove calls to this feature. [2017-05-31]"
			-- Attached version of Current.
			-- (Can be used during transitional period to convert
			-- non-void-safe classes to void-safe ones.)
			-- (from ANY)
		do
			Result := Current
		end

	frozen default: detachable HEAP_PRIORITY_QUEUE [G]
			-- Default value of object's type
			-- (from ANY)
		do
		end

	frozen default_pointer: POINTER
			-- Default value of type POINTER
			-- (Avoid the need to write p.default for
			-- some p of type POINTER.)
			-- (from ANY)
		do
		ensure -- from ANY
			instance_free: class
		end

	default_rescue
			-- Process exception for routines with no Rescue clause.
			-- (Default: do nothing.)
			-- (from ANY)
		do
		end

	frozen do_nothing
			-- Execute a null action.
			-- (from ANY)
		do
		ensure -- from ANY
			instance_free: class
		end
	
feature -- Inapplicable

	replace (v: like item)
			-- Replace current item by v.
		require -- from ACTIVE
			writable: writable
			replaceable: replaceable
		do
		ensure -- from ACTIVE
			item_replaced: item = v
		end
	
feature {HEAP_PRIORITY_QUEUE} -- Implementation

	force_i_th (v: G; i: INTEGER_32)
		require
			valid_index: i >= Lower and i <= count + Lower
			valid_upper: i = count + Lower implies count < capacity
		do
			area.force (v, i - Lower)
		end

	i_th (i: INTEGER_32): G
		require
			valid_index: area.valid_index (i - Lower)
		do
			Result := area.item (i - Lower)
		end

	put_i_th (v: G; i: INTEGER_32)
		require
			valid_index: area.valid_index (i - Lower)
		do
			area.put (v, i - Lower)
		end
	
feature -- Iteration

	new_cursor: HEAP_PRIORITY_QUEUE_ITERATION_CURSOR [G]
			-- Fresh cursor associated with current structure
		do
			create Result.make (Current)
		ensure -- from ITERABLE
			result_attached: Result /= Void
		end
	
feature -- Output

	Io: STD_FILES
			-- Handle to standard file setup
			-- (from ANY)
		once
			create Result;
			Result.set_output_default
		ensure -- from ANY
			instance_free: class
			io_not_void: Result /= Void
		end

	out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from ANY)
		do
			Result := tagged_out
		ensure -- from ANY
			out_not_void: Result /= Void
		end

	print (o: detachable ANY)
			-- Write terse external representation of o
			-- on standard output.
			-- (from ANY)
		local
			s: READABLE_STRING_8
		do
			if attached o then
				s := o.out
				if attached {READABLE_STRING_32} s as s32 then
					Io.put_string_32 (s32)
				elseif attached {READABLE_STRING_8} s as s8 then
					Io.put_string (s8)
				else
					Io.put_string_32 (s.as_string_32)
				end
			end
		ensure -- from ANY
			instance_free: class
		end

	frozen tagged_out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			tagged_out_not_void: Result /= Void
		end
	
feature -- Platform

	Operating_environment: OPERATING_ENVIRONMENT
			-- Objects available from the operating system
			-- (from ANY)
		once
			create Result
		ensure -- from ANY
			instance_free: class
			operating_environment_not_void: Result /= Void
		end
	
feature {NONE} -- Retrieval

	frozen internal_correct_mismatch
			-- Called from runtime to perform a proper dynamic dispatch on correct_mismatch
			-- from MISMATCH_CORRECTOR.
			-- (from ANY)
		local
			l_msg: STRING_32
			l_exc: EXCEPTIONS
		do
			if attached {MISMATCH_CORRECTOR} Current as l_corrector then
				l_corrector.correct_mismatch
			else
				create l_msg.make_from_string ("Mismatch: ".as_string_32)
				create l_exc;
				l_msg.append (generating_type.name_32);
				l_exc.raise_retrieval_exception (l_msg)
			end
		end
	
invariant
		-- from DISPENSER
	readable_definition: readable = not is_empty
	writable_definition: writable = not is_empty

		-- from ACTIVE
	writable_constraint: writable implies readable
	empty_constraint: is_empty implies (not readable) and (not writable)

		-- from ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)

		-- from FINITE
	empty_definition: is_empty = (count = 0)

		-- from RESIZABLE
	increase_by_at_least_one: Minimal_increase >= 1

		-- from BOUNDED
	valid_count: count <= capacity
	full_definition: full = (count = capacity)

note
	copyright: "Copyright (c) 1984-2018, Eiffel Software and others"
	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
	source: "[
		Eiffel Software
		5949 Hollister Ave., Goleta, CA 93117 USA
		Telephone 805-685-1006, Fax 805-685-6869
		Website http://www.eiffel.com
		Customer support http://support.eiffel.com
	]"

end -- class HEAP_PRIORITY_QUEUE

Generated by ISE EiffelStudio