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 interface
	HEAP_PRIORITY_QUEUE [G -> COMPARABLE]

create 
	make (n: INTEGER_32)
			-- Allocate heap space.

	make_from_iterable (other: ITERABLE [G])
			-- Create a priority queue with all items obtained from other.

feature -- Access

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

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

	has (v: G): BOOLEAN
			-- Does structure include v?
			-- (Reference or object equality,
			-- based on object_comparison.)
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty

	item: G
			-- Entry at top of heap.
		require -- from ACTIVE
			readable: readable
	
feature -- Measurement

	additional_space: INTEGER_32
			-- Proposed number of additional items
			-- (from RESIZABLE)
		ensure -- from RESIZABLE
			at_least_one: Result >= 1

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

	count: INTEGER_32
			-- Number of items
		ensure -- from FINITE
			count_non_negative: Result >= 0

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

	index_set: INTEGER_INTERVAL
			-- Range of acceptable indexes
		ensure then
			count_definition: Result.count = count

	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.)
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
	
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)
		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)

	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)
		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))

	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
		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)

	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
		ensure -- from ANY
			symmetric: Result implies other ~ Current
			consistent: standard_is_equal (other) implies Result

	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)
		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))

	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
		ensure -- from ANY
			same_type: Result implies same_type (other)
			symmetric: Result implies other.standard_is_equal (Current)
	
feature -- Status report

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

	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

	extendible: BOOLEAN
			-- May items be added?

	full: BOOLEAN
			-- Is structure full?
			-- (from BOUNDED)
		require -- from  BOX
			True

	is_empty: BOOLEAN
			-- Is structure empty?
			-- (from FINITE)
		require -- from  CONTAINER
			True

	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)

	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)

	replaceable: BOOLEAN
			-- Can current item be replaced?

	resizable: BOOLEAN
			-- May capacity be changed? (Answer: yes.)
			-- (from RESIZABLE)

	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
		ensure -- from ANY
			definition: Result = (conforms_to (other) and other.conforms_to (Current))

	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: 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: 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)
		require -- from DISPENSER
			s_not_void: s /= Void
			extendible: extendible

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

	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

	force (v: like item)
			-- Add item v at its proper position.
		require -- from DISPENSER
			extendible: extendible
		ensure -- from DISPENSER
			item_inserted: is_inserted (v)

	put (v: like item)
			-- Insert item v at its proper position.
		require -- from COLLECTION
			extendible: extendible
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
	
feature -- Removal

	prune (v: G)
			-- Remove first occurrence of v if any.
		require -- from COLLECTION
			prunable: Prunable

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

	remove
			-- Remove item of highest value.
		require -- from ACTIVE
			prunable: Prunable
			writable: writable

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

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

	grow (i: INTEGER_32)
			-- Ensure that capacity is at least i.
		require -- from RESIZABLE
			resizable: resizable
		ensure -- from RESIZABLE
			new_capacity: capacity >= i

	trim
			-- Decrease capacity to the minimum value.
			-- Apply to reduce allocated storage.
		require -- from  RESIZABLE
			True
		ensure -- from RESIZABLE
			same_count: count = old count
			minimal_capacity: capacity = count
		ensure then
			same_items: linear_representation.is_equal (old linear_representation)
	
feature -- Conversion

	linear_representation: ARRAYED_LIST [G]
			-- Representation as a linear structure
			-- (Sorted according to decreasing priority)
	
feature -- Duplication

	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)
		ensure -- from ANY
			is_equal: Current ~ other

	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
		ensure -- from ANY
			deep_equal: deep_equal (Current, other)

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

	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)
		ensure -- from ANY
			is_standard_equal: standard_is_equal (other)

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

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

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

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

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

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

	replace (v: like item)
			-- Replace current item by v.
		require -- from ACTIVE
			writable: writable
			replaceable: replaceable
		ensure -- from ACTIVE
			item_replaced: item = v
	
feature -- Iteration

	new_cursor: HEAP_PRIORITY_QUEUE_ITERATION_CURSOR [G]
			-- Fresh cursor associated with current structure
		ensure -- from ITERABLE
			result_attached: Result /= Void
	
feature -- Output

	Io: STD_FILES
			-- Handle to standard file setup
			-- (from ANY)
		ensure -- from ANY
			instance_free: class
			io_not_void: Result /= Void

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

	print (o: detachable ANY)
			-- Write terse external representation of o
			-- on standard output.
			-- (from ANY)
		ensure -- from ANY
			instance_free: class

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

	Operating_environment: OPERATING_ENVIRONMENT
			-- Objects available from the operating system
			-- (from ANY)
		ensure -- from ANY
			instance_free: class
			operating_environment_not_void: Result /= Void
	
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

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