note
	description: "[
		Sequences of values, all of the same type or of a conforming one,
		accessible through integer indices in a contiguous interval.
	]"
	library: "Free implementation of ELKS library"
	status: "See notice at end of class."
	legal: "See notice at end of class."
	date: "$Date: 2020-02-18 09:43:52 +0000 (Tue, 18 Feb 2020) $"
	revision: "$Revision: 103939 $"

class 
	ARRAY [G]

create 
	make_empty,
	make,
	make_filled,
	make_from_array,
	make_from_special,
	make_from_cil

convert
	to_cil: {NATIVE_ARRAY [G]},
	to_special: {SPECIAL [G]},
	make_from_cil ({NATIVE_ARRAY [G]})

feature -- Initialization

	make (min_index, max_index: INTEGER_32)
		obsolete " `make' is not void-safe statically. Use `make_empty' or `make_filled' instead. [2017-05-31]"
			-- Allocate array; set index interval to
			-- min_index .. max_index; set all values to default.
			-- (Make array empty if min_index = max_index + 1).
		require
			valid_bounds: min_index <= max_index + 1
			has_default: min_index <= max_index implies ({G}).has_default
		do
			lower := min_index
			upper := max_index
			if min_index <= max_index then
				make_filled_area (({G}).default, max_index - min_index + 1)
			else
				make_empty_area (0)
			end
		ensure
			lower_set: lower = min_index
			upper_set: upper = max_index
			items_set: all_default
		end

	make_empty
			-- Allocate empty array starting at 1.
		do
			lower := 1
			upper := 0
			make_empty_area (0)
		ensure
			lower_set: lower = 1
			upper_set: upper = 0
			items_set: all_default
		end

	make_filled (a_default_value: G; min_index, max_index: INTEGER_32)
			-- Allocate array; set index interval to
			-- min_index .. max_index; set all values to default.
			-- (Make array empty if min_index = max_index + 1).
		require
			valid_bounds: min_index <= max_index + 1
		local
			n: INTEGER_32
		do
			lower := min_index
			upper := max_index
			if min_index <= max_index then
				n := max_index - min_index + 1
			end
			make_filled_area (a_default_value, n)
		ensure
			lower_set: lower = min_index
			upper_set: upper = max_index
			items_set: filled_with (a_default_value)
		end

	make_from_array (a: ARRAY [G])
			-- Initialize from the items of a.
			-- (Useful in proper descendants of class ARRAY,
			-- to initialize an array-like object from a manifest array.)
		require
			array_exists: a /= Void
		do
			set_area (a.area)
			lower := a.lower
			upper := a.upper
		ensure
			shared: area = a.area
			lower_set: lower = a.lower
			upper_set: upper = a.upper
		end

	make_from_cil (na: NATIVE_ARRAY [like item])
			-- Initialize array from na.
		require
			is_dotnet: {PLATFORM}.is_dotnet
			na_not_void: na /= Void
		do
			create area.make_from_native_array (na)
			lower := 1
			upper := area.count
		end

	make_from_special (a: SPECIAL [G])
			-- Initialize Current from items of a.
		require
			special_attached: a /= Void
		do
			set_area (a)
			lower := 1
			upper := a.count
		ensure
			shared: area = a
			lower_set: lower = 1
			upper_set: upper = a.count
		end
	
feature {NONE} -- Initialization

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

	make_empty_area (n: INTEGER_32)
			-- Creates a special object for n entries.
			-- (from TO_SPECIAL)
		require -- from TO_SPECIAL
			non_negative_argument: n >= 0
		do
			create area.make_empty (n)
		ensure -- from TO_SPECIAL
			area_allocated: area /= Void
			capacity_set: area.capacity = n
			count_set: area.count = 0
		end

	make_filled_area (a_default_value: G; n: INTEGER_32)
			-- Creates a special object for n entries.
			-- (from TO_SPECIAL)
		require -- from TO_SPECIAL
			non_negative_argument: n >= 0
		do
			create area.make_filled (a_default_value, n)
		ensure -- from TO_SPECIAL
			area_allocated: area /= Void
			capacity_set: area.capacity = n
			count_set: area.count = n
			area_filled: area.filled_with (a_default_value, 0, n - 1)
		end
	
feature -- Access

	area: SPECIAL [G]
			-- Special data zone.
			-- (from TO_SPECIAL)

	at alias "@" (i: INTEGER_32): G assign put
			-- Entry at index i, if in index interval.
			-- Was declared in ARRAY as synonym of item.
		require -- from TABLE
			valid_key: valid_index (i)
		require -- from TO_SPECIAL
			valid_index: valid_index (i)
		do
			Result := area.item (i - lower)
		end

	entry (i: INTEGER_32): G
			-- Entry at index i, if in index interval.
		require
			valid_key: valid_index (i)
		do
			Result := item (i)
		end

	generating_type: TYPE [detachable ARRAY [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 v appear in array?
			-- (Reference or object equality,
			-- based on object_comparison.)
		local
			i, nb: INTEGER_32
			l_area: like area
		do
			l_area := area
			nb := upper - lower
			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 alias "[]" (i: INTEGER_32): G assign put
			-- Entry at index i, if in index interval.
			-- Was declared in ARRAY as synonym of at.
		require -- from TABLE
			valid_key: valid_index (i)
		require -- from READABLE_INDEXABLE
			valid_index: valid_index (i)
		require -- from TO_SPECIAL
			valid_index: valid_index (i)
		do
			Result := area.item (i - lower)
		end

	new_cursor: ARRAY_ITERATION_CURSOR [G]
			-- Fresh cursor associated with current structure
		require -- from  ITERABLE
			True
		do
			create Result.make (Current)
		ensure -- from ITERABLE
			result_attached: Result /= Void
		end
	
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 available indices.
			-- Was declared in ARRAY as synonym of count.
		require -- from  BOUNDED
			True
		do
			Result := upper - lower + 1
		ensure -- from BOUNDED
			capacity_non_negative: Result >= 0
		ensure then
			consistent_with_bounds: Result = upper - lower + 1
		end

	count: INTEGER_32
			-- Number of available indices.
			-- Was declared in ARRAY as synonym of capacity.
		require -- from  FINITE
			True
		do
			Result := upper - lower + 1
		ensure -- from FINITE
			count_non_negative: Result >= 0
		ensure then
			consistent_with_bounds: Result = upper - lower + 1
		end

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

	index_set: INTEGER_INTERVAL
		obsolete "Use `lower' and `upper' instead. [2017-05-31]"
			-- Range of acceptable indexes.
			-- (from READABLE_INDEXABLE)
		do
			create Result.make (lower, upper)
		ensure -- from READABLE_INDEXABLE
			not_void: Result /= Void
			empty_if_not_in_order: (lower > upper) implies Result.is_empty
			same_lower_if_not_empty: (lower <= upper) implies Result.lower = lower
			same_upper_if_not_empty: (lower <= upper) implies Result.upper = upper
		end

	lower: INTEGER_32
			-- Minimum index.

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

	occurrences (v: G): INTEGER_32
			-- Number of times v appears in structure.
		local
			i: INTEGER_32
		do
			if object_comparison then
				from
					i := lower
				until
					i > upper
				loop
					if item (i) ~ v then
						Result := Result + 1
					end
					i := i + 1
				end
			else
				from
					i := lower
				until
					i > upper
				loop
					if item (i) = v then
						Result := Result + 1
					end
					i := i + 1
				end
			end
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
		end

	upper: INTEGER_32
			-- Maximum index.
	
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: ARRAY [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 array made of the same items as other?
		require -- from ANY
			other_not_void: other /= Void
		local
			i: INTEGER_32
		do
			if other = Current then
				Result := True
			elseif lower = other.lower and then upper = other.upper and then object_comparison = other.object_comparison then
				if object_comparison then
					from
						Result := True
						i := lower
					until
						not Result or i > upper
					loop
						Result := item (i) ~ other.item (i)
						i := i + 1
					end
				else
					Result := area.same_items (other.area, 0, 0, count)
				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: ARRAY [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 -- Status report

	all_default: BOOLEAN
			-- Are all items set to default values?
		do
			if count > 0 then
				Result := ({G}).has_default and then area.filled_with (({G}).default, 0, upper - lower)
			else
				Result := True
			end
		ensure
			definition: Result = (count = 0 or else ((not attached item (upper) as i or else i = ({G}).default) and subarray (lower, upper - 1).all_default))
		end

	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?
			-- (Answer: no, although array may be resized.)
		do
			Result := False
		end

	filled_with (v: G): BOOLEAN
			-- Are all items set to v?
		do
			Result := area.filled_with (v, 0, upper - lower)
		ensure
			definition: Result = (count = 0 or else (item (upper) = v and subarray (lower, upper - 1).filled_with (v)))
		end

	full: BOOLEAN
			-- Is structure filled to capacity?
			-- (Answer: yes)
		require -- from  BOX
			True
		do
			Result := True
		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
			-- May items be removed?
			-- (Answer: no.)
		do
			Result := False
		end

	resizable: BOOLEAN
			-- Can array be resized automatically?
		require -- from  BOUNDED
			True
		do
			Result := ({G}).has_default
		end

	same_items (other: like Current): BOOLEAN
			-- Do other and Current have same items?
		require
			other_not_void: other /= Void
		do
			if count = other.count then
				Result := area.same_items (other.area, 0, 0, count)
			end
		ensure
			definition: Result = (count = other.count and then (count = 0 or else (item (upper) = other.item (other.upper) and subarray (lower, upper - 1).same_items (other.subarray (other.lower, other.upper - 1)))))
		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

	valid_index (i: INTEGER_32): BOOLEAN
			-- Is i within the bounds of the array?
		require -- from  READABLE_INDEXABLE
			True
		require -- from  TABLE
			True
		require -- from  TO_SPECIAL
			True
		do
			Result := (lower <= i) and then (i <= upper)
		ensure -- from READABLE_INDEXABLE
			only_if_in_index_set: Result implies (lower <= i and i <= upper)
		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

	enter (v: like item; i: INTEGER_32)
			-- Replace i-th entry, if in index interval, by v.
		require
			valid_key: valid_index (i)
		do
			area.put (v, i - lower)
		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

	fill_with (v: G)
			-- Set items between lower and upper with v.
		do
			area.fill_with (v, 0, upper - lower)
		ensure
			same_capacity: capacity = old capacity
			count_definition: count = old count
			filled: filled_with (v)
		end

	force (v: like item; i: INTEGER_32)
			-- Assign item v to i-th entry.
			-- Resize the array if i falls out of currently defined bounds; preserve existing items.
			-- In void-safe mode, if ({G}).has_default does not hold, then you can only insert between
			-- lower - 1 and upper + 1 positions in the ARRAY.
		require
			has_default_if_too_low: (i < lower - 1 and lower /= {like lower}.min_value) implies ({G}).has_default
			has_default_if_too_high: (i > upper + 1 and upper /= {like upper}.max_value) implies ({G}).has_default
		local
			old_size, new_size: INTEGER_32
			new_lower, new_upper: INTEGER_32
			l_count, l_offset: INTEGER_32
			l_increased_by_one: BOOLEAN
		do
			new_lower := lower.min (i)
			new_upper := upper.max (i)
			new_size := new_upper - new_lower + 1
			l_increased_by_one := (i = upper + 1) or (i = lower - 1)
			if empty_area then
				make_empty_area (new_size.max (additional_space))
				if new_lower < lower then
					area.extend (v)
					if not l_increased_by_one then
						area.fill_with (({G}).default, 1, new_size - 1)
					end
				else
					if not l_increased_by_one then
						area.fill_with (({G}).default, 0, new_size - 2)
					end;
					area.extend (v)
				end
			else
				old_size := area.capacity
				if new_size > old_size then
					set_area (area.aliased_resized_area (new_size.max (old_size + additional_space)))
				end
				if new_lower < lower then
					l_offset := lower - new_lower
					l_count := capacity
					if not l_increased_by_one and l_offset > l_count then
						area.fill_with (({G}).default, l_count, l_offset - 1)
					end;
					area.move_data (0, l_offset, l_count)
					if not l_increased_by_one then
						area.fill_with (({G}).default, 1, l_offset - 1)
					end;
					area.put (v, 0)
				else
					if new_size > area.count then
						if not l_increased_by_one then
							area.fill_with (({G}).default, area.count, new_size - 2)
						end;
						area.extend (v)
					else
						area.put (v, i - lower)
					end
				end
			end
			lower := new_lower
			upper := new_upper
		ensure
			inserted: item (i) = v
			higher_count: count >= old count
			lower_set: lower = (old lower).min (i)
			upper_set: upper = (old upper).max (i)
		end

	force_and_fill (v: like item; i: INTEGER_32)
			-- Assign item v to i-th entry.
			-- If i falls out of currently defined bounds:
			-- 	- Resize array as needed.
			-- 	- Fill in any new entry (in addition to the one at position i with value v).
			-- 	- Preserve existing items.
		local
			old_size, new_size: INTEGER_32
			new_lower, new_upper: INTEGER_32
			l_offset: INTEGER_32
		do
			new_lower := lower.min (i)
			new_upper := upper.max (i)
			new_size := new_upper - new_lower + 1
			old_size := area.capacity
			if old_size = 0 then
				make_empty_area (new_size.max (additional_space));
				area.fill_with (v, 0, new_size - 1)
			else
				if new_size > old_size then
					set_area (area.aliased_resized_area (new_size.max (old_size + additional_space)))
				end
				if new_lower < lower then
					l_offset := lower - new_lower;
					area.move_data (0, l_offset, capacity);
					area.fill_with (v, 0, l_offset - 1)
				elseif new_size > area.count then
					area.fill_with (v, area.count, new_size - 1)
				else
					area.put (v, i - lower)
				end
			end
			lower := new_lower
			upper := new_upper
		ensure
			inserted: item (i) = v
			filled_below_lower: ∀ c: i |..| old lower ¦
					c < old lower implies item (c) = v
			filled_above_upper: ∀ c: old upper |..| i ¦
					c > old upper implies item (c) = v
			higher_count: count >= old count
			lower_set: lower = (old lower).min (i)
			upper_set: upper = (old upper).max (i)
		end

	put (v: like item; i: INTEGER_32)
			-- Replace i-th entry, if in index interval, by v.
		require -- from TABLE
			valid_key: valid_index (i)
		require -- from TABLE
			valid_key: valid_index (i)
		require -- from TO_SPECIAL
			valid_index: valid_index (i)
		do
			area.put (v, i - lower)
		ensure -- from TABLE
			inserted: item (i) = v
		ensure -- from TO_SPECIAL
			inserted: item (i) = v
		end

	subcopy (other: ARRAY [like item]; start_pos, end_pos, index_pos: INTEGER_32)
			-- Copy items of other within bounds start_pos and end_pos
			-- to current array starting at index index_pos.
		require
			other_not_void: other /= Void
			valid_start_pos: start_pos >= other.lower
			valid_end_pos: end_pos <= other.upper
			valid_bounds: start_pos <= end_pos + 1
			valid_index_pos: index_pos >= lower
			enough_space: (upper - index_pos) >= (end_pos - start_pos)
		do
			area.copy_data (other.area, start_pos - other.lower, index_pos - lower, end_pos - start_pos + 1)
		end
	
feature {ARRAY} -- Element change

	set_area (other: like area)
			-- Make other the new area.
			-- (from TO_SPECIAL)
		do
			area := other
		ensure -- from TO_SPECIAL
			area_set: area = other
		end
	
feature -- Removal

	clear_all
			-- Reset all items to default values.
		require
			has_default: ({G}).has_default
		do
			area.fill_with (({G}).default, 0, area.count - 1)
		ensure
			stable_lower: lower = old lower
			stable_upper: upper = old upper
			default_items: all_default
		end

	discard_items
			-- Reset all items to default values with reallocation.
		require
			has_default: ({G}).has_default
		do
			create area.make_filled (({G}).default, capacity)
		ensure
			default_items: all_default
		end

	keep_head (n: INTEGER_32)
			-- Remove all items except for the first n;
			-- do nothing if n >= count.
		require
			non_negative_argument: n >= 0
		do
			if n < count then
				upper := lower + n - 1
				area := area.aliased_resized_area (n)
			end
		ensure
			new_count: count = n.min (old count)
			same_lower: lower = old lower
		end

	keep_tail (n: INTEGER_32)
			-- Remove all items except for the last n;
			-- do nothing if n >= count.
		require
			non_negative_argument: n >= 0
		local
			nb: INTEGER_32
		do
			nb := count
			if n < nb then
				area.overlapping_move (nb - n, 0, n)
				lower := upper - n + 1
				area := area.aliased_resized_area (n)
			end
		ensure
			new_count: count = n.min (old count)
			same_upper: upper = old upper
		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_head (n: INTEGER_32)
			-- Remove first n items;
			-- if n > count, remove all.
		require
			n_non_negative: n >= 0
		do
			if n > count then
				lower := upper + 1
				area := area.aliased_resized_area (0)
			else
				keep_tail (count - n)
			end
		ensure
			new_count: count = (old count - n).max (0)
			same_upper: upper = old upper
		end

	remove_tail (n: INTEGER_32)
			-- Remove last n items;
			-- if n > count, remove all.
		require
			n_non_negative: n >= 0
		do
			if n > count then
				upper := lower - 1
				area := area.aliased_resized_area (0)
			else
				keep_head (count - n)
			end
		ensure
			new_count: count = (old count - n).max (0)
			same_lower: lower = old lower
		end

	wipe_out
		obsolete "Not applicable since not `prunable'. Use `discard_items' instead. [2017-05-31]"
			-- Make array empty.
		require -- from COLLECTION
			prunable: prunable
		do
			discard_items
		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

	conservative_resize (min_index, max_index: INTEGER_32)
		obsolete " `conservative_resize' is not void-safe statically. Use `conservative_resize_with_default' instead. [2017-05-31]"
			-- Rearrange array so that it can accommodate
			-- indices down to min_index and up to max_index.
			-- Do not lose any previously entered item.
		require
			good_indices: min_index <= max_index
			has_default: ({G}).has_default
		do
			conservative_resize_with_default (({G}).default, min_index, max_index)
		ensure
			no_low_lost: lower = min_index or else lower = old lower
			no_high_lost: upper = max_index or else upper = old upper
		end

	conservative_resize_with_default (a_default_value: G; min_index, max_index: INTEGER_32)
			-- Rearrange array so that it can accommodate
			-- indices down to min_index and up to max_index.
			-- Do not lose any previously entered item.
		require
			good_indices: min_index <= max_index
		local
			new_size: INTEGER_32
			new_lower, new_upper: INTEGER_32
			offset: INTEGER_32
		do
			if empty_area then
				set_area (area.aliased_resized_area_with_default (a_default_value, max_index - min_index + 1))
				lower := min_index
				upper := max_index
			else
				new_lower := min_index.min (lower)
				new_upper := max_index.max (upper)
				new_size := new_upper - new_lower + 1
				if new_size > area.count then
					set_area (area.aliased_resized_area_with_default (a_default_value, new_size))
				end
				if new_lower < lower then
					offset := lower - new_lower;
					area.move_data (0, offset, upper - lower + 1);
					area.fill_with (a_default_value, 0, offset - 1)
				end
				lower := new_lower
				upper := new_upper
			end
		ensure
			no_low_lost: lower = min_index or else lower = old lower
			no_high_lost: upper = max_index or else upper = old upper
		end

	grow (i: INTEGER_32)
			-- Change the capacity to at least i.
		require -- from RESIZABLE
			resizable: resizable
		do
			if i > capacity then
				conservative_resize_with_default (({G}).default, lower, upper + i - capacity)
			end
		ensure -- from RESIZABLE
			new_capacity: capacity >= i
		end

	rebase (a_lower: like lower)
			-- Without changing the actual content of Current we set lower to a_lower
			-- and upper accordingly to a_lower + count - 1.
		local
			l_old_lower: like lower
		do
			l_old_lower := lower
			lower := a_lower
			upper := a_lower + (upper - l_old_lower)
		ensure
			lower_set: lower = a_lower
			upper_set: upper = a_lower + old count - 1
		end

	resize (min_index, max_index: INTEGER_32)
		obsolete "Use `conservative_resize_with_default' instead as future versions will implement `resize' as specified in ELKS. [2017-05-31]"
			-- Rearrange array so that it can accommodate
			-- indices down to min_index and up to max_index.
			-- Do not lose any previously entered item.
		require
			good_indices: min_index <= max_index
			has_default: ({G}).has_default
		do
			conservative_resize_with_default (({G}).default, min_index, max_index)
		ensure
			no_low_lost: lower = min_index or else lower = old lower
			no_high_lost: upper = max_index or else upper = old upper
		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 < area.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: same_items (old twin)
		end
	
feature -- Conversion

	linear_representation: LINEAR [G]
			-- Representation as a linear structure.
		local
			temp: ARRAYED_LIST [G]
			i: INTEGER_32
		do
			create temp.make (capacity)
			from
				i := lower
			until
				i > upper
			loop
				temp.extend (item (i))
				i := i + 1
			end
			Result := temp
		end

	to_c: ANY
			-- Address of actual sequence of values,
			-- for passing to external (non-Eiffel) routines.
		require
			not_is_dotnet: not {PLATFORM}.is_dotnet
		do
			Result := area
		end

	to_cil: NATIVE_ARRAY [G]
			-- Address of actual sequence of values,
			-- for passing to external (non-Eiffel) routines.
		require
			is_dotnet: {PLATFORM}.is_dotnet
		do
			Result := area.native_array
		ensure
			to_cil_not_void: Result /= Void
		end

	to_special: SPECIAL [G]
			-- 'area'.
		do
			Result := area
		ensure
			to_special_not_void: Result /= Void
		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)
			-- Reinitialize by copying all the items of other.
			-- (This is also used by clone.)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		do
			if other /= Current then
				standard_copy (other)
				set_area (other.area.twin)
			end
		ensure -- from ANY
			is_equal: Current ~ other
		ensure then
			equal_areas: area ~ other.area
		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: ARRAY [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: ARRAY [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

	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: ARRAY [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: ARRAY [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

	subarray (start_pos, end_pos: INTEGER_32): ARRAY [G]
			-- Array made of items of current array within
			-- bounds start_pos and end_pos.
		require
			valid_start_pos: lower <= start_pos
			valid_end_pos: end_pos <= upper
			valid_bounds: (start_pos <= end_pos) or (start_pos = end_pos + 1)
		do
			if start_pos <= end_pos then
				create Result.make_filled (item (start_pos), start_pos, end_pos);
				Result.subcopy (Current, start_pos, end_pos, start_pos)
			else
				create Result.make_empty;
				Result.rebase (start_pos)
			end
		ensure
			lower: Result.lower = start_pos
			upper: Result.upper = end_pos
		end

	frozen twin: ARRAY [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 ARRAY [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 ARRAY [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

	bag_put (v: G)
			-- Ensure that structure includes v.
			-- (from TABLE)
		require -- from COLLECTION
			extendible: extendible
		do
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		end

	extend (v: G)
			-- Add v to structure.
			-- (Precondition is False.)
		require -- from COLLECTION
			extendible: extendible
		do
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		end

	prune (v: G)
			-- Remove first occurrence of v if any.
			-- (Precondition is False.)
		require -- from COLLECTION
			prunable: prunable
		do
		end
	
feature {NONE} -- Implementation

	empty_area: BOOLEAN
			-- Is area empty?
		do
			Result := area.capacity = 0
		end
	
feature -- Iteration

	do_all (action: PROCEDURE [G])
			-- Apply action to every item, from first to last.
			-- Semantics not guaranteed if action changes the structure;
			-- in such a case, apply iterator to clone of structure instead.
		require
			action_not_void: action /= Void
		do
			area.do_all_in_bounds (action, 0, count - 1)
		end

	do_all_with_index (action: PROCEDURE [G, INTEGER_32])
			-- Apply action to every item, from first to last.
			-- action receives item and its index.
			-- Semantics not guaranteed if action changes the structure;
			-- in such a case, apply iterator to clone of structure instead.
		local
			i, j, nb: INTEGER_32
			l_area: like area
		do
			from
				i := 0
				j := lower
				nb := count - 1
				l_area := area
			until
				i > nb
			loop
				action.call ([l_area.item (i), j])
				j := j + 1
				i := i + 1
			end
		end

	do_if (action: PROCEDURE [G]; test: FUNCTION [G, BOOLEAN])
			-- Apply action to every item that satisfies test, from first to last.
			-- Semantics not guaranteed if action or test changes the structure;
			-- in such a case, apply iterator to clone of structure instead.
		require
			action_not_void: action /= Void
			test_not_void: test /= Void
		do
			area.do_if_in_bounds (action, test, 0, count - 1)
		end

	do_if_with_index (action: PROCEDURE [G, INTEGER_32]; test: FUNCTION [G, INTEGER_32, BOOLEAN])
			-- Apply action to every item that satisfies test, from first to last.
			-- action and test receive the item and its index.
			-- Semantics not guaranteed if action or test changes the structure;
			-- in such a case, apply iterator to clone of structure instead.
		local
			i, j, nb: INTEGER_32
			l_area: like area
		do
			from
				i := 0
				j := lower
				nb := count - 1
				l_area := area
			until
				i > nb
			loop
				if test.item ([l_area.item (i), j]) then
					action.call ([l_area.item (i), j])
				end
				j := j + 1
				i := i + 1
			end
		end

	for_all (test: FUNCTION [G, BOOLEAN]): BOOLEAN
			-- Is test true for all items?
		require
			test_not_void: test /= Void
		do
			Result := area.for_all_in_bounds (test, 0, count - 1)
		end

	there_exists (test: FUNCTION [G, BOOLEAN]): BOOLEAN
			-- Is test true for at least one item?
		require
			test_not_void: test /= Void
		do
			Result := area.there_exists_in_bounds (test, 0, count - 1)
		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
	area_exists: area /= Void
	consistent_size: capacity = upper - lower + 1
	non_negative_count: count >= 0

		-- from RESIZABLE
	increase_by_at_least_one: Minimal_increase >= 1

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

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

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

		-- from READABLE_INDEXABLE
	consistent_boundaries: lower <= upper or else lower = upper + 1

note
	copyright: "Copyright (c) 1984-2020, 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 ARRAY

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