note
	description: "[
		Sequences of 32-bit characters, accessible through integer indices
		in a contiguous range.
	]"
	library: "Free implementation of ELKS library"
	status: "See notice at end of class."
	legal: "See notice at end of class."
	date: "$Date: 2020-05-19 14:21:28 +0000 (Tue, 19 May 2020) $"
	revision: "$Revision: 104256 $"

class 
	STRING_32

create 
	make,
	make_empty,
	make_filled,
	make_from_string,
	make_from_string_general,
	make_from_c,
	make_from_c_pointer,
	make_from_c_byte_array,
	make_from_cil,
	make_from_separate

convert
	to_cil: {SYSTEM_STRING},
	make_from_cil ({SYSTEM_STRING}),
	as_string_8: {READABLE_STRING_8,
		STRING_8}

feature -- Initialization

	adapt (s: STRING_32): like Current
			-- Object of a type conforming to the type of s,
			-- initialized with attributes from s
		do
			Result := new_string (0);
			Result.share (s)
		ensure
			adapt_not_void: Result /= Void
			shared_implementation: Result.shared_with (s)
		end

	from_c (c_string: POINTER)
			-- Reset contents of string from contents of c_string,
			-- a string created by some C function.
		require
			c_string_exists: c_string /= default_pointer
		local
			l_count: INTEGER_32
		do
			C_string_provider.set_shared_from_pointer (c_string)
			l_count := C_string_provider.count
			grow (l_count + 1)
			count := l_count
			reset_hash_codes;
			C_string_provider.read_string_into (Current)
		ensure
			no_zero_byte: not has ('%U'.to_character_32)
		end

	from_c_substring (c_string: POINTER; start_pos, end_pos: INTEGER_32)
			-- Reset contents of string from substring of c_string,
			-- a string created by some C function.
		require
			c_string_exists: c_string /= default_pointer
			start_position_big_enough: start_pos >= 1
			end_position_big_enough: start_pos <= end_pos + 1
		local
			l_count: INTEGER_32
		do
			l_count := end_pos - start_pos + 1;
			C_string_provider.set_shared_from_pointer_and_count (c_string + (start_pos - 1), l_count)
			grow (l_count + 1)
			count := l_count
			reset_hash_codes;
			C_string_provider.read_substring_into (Current, 1, l_count)
		ensure
			valid_count: count = end_pos - start_pos + 1
		end

	make (n: INTEGER_32)
			-- Allocate space for at least n characters.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_GENERAL
			non_negative_size: n >= 0
		do
			count := 0
			internal_hash_code := 0
			create area.make_filled ('%U'.to_character_32, n + 1)
		ensure -- from READABLE_STRING_GENERAL
			empty_string: count = 0
			area_allocated: capacity >= n
		end

	make_empty
			-- Create empty string.
			-- (from READABLE_STRING_GENERAL)
		do
			make (0)
		ensure -- from READABLE_STRING_GENERAL
			empty: count = 0
			area_allocated: capacity >= 0
		end

	make_filled (c: CHARACTER_32; n: INTEGER_32)
			-- Create string of length n filled with c.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			valid_count: n >= 0
		do
			make (n)
			fill_character (c)
		ensure -- from READABLE_STRING_32
			count_set: count = n
			area_allocated: capacity >= n
			filled: occurrences (c) = count
		end

	make_from_c (c_string: POINTER)
			-- Initialize from contents of c_string,
			-- a string created by some C function.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			c_string_exists: c_string /= default_pointer
		local
			l_count: INTEGER_32
		do
			C_string_provider.set_shared_from_pointer (c_string)
			l_count := C_string_provider.count
			create area.make_filled ('%U'.to_character_32, l_count + 1)
			count := l_count
			internal_hash_code := 0;
			C_string_provider.read_substring_into_character_32_area (area, 1, l_count)
		end

	make_from_cil (a_system_string: detachable SYSTEM_STRING)
			-- Initialize Current with a_system_string.
		require -- from READABLE_STRING_32
			is_dotnet: {PLATFORM}.is_dotnet
		local
			l_count: INTEGER_32
		do
			if a_system_string /= Void then
				l_count := a_system_string.length + Dotnet_convertor.escape_count (a_system_string)
			end
			make (l_count)
			if l_count > 0 and then a_system_string /= Void then
				set_count (l_count);
				Dotnet_convertor.read_system_string_into (a_system_string, Current)
			end
		end

	make_from_string (s: READABLE_STRING_32)
			-- Initialize from the characters of s.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			string_exists: s /= Void
		do
			area := s.area
			count := s.count
			internal_hash_code := 0
			if Current /= s then
				create area.make_empty (count + 1);
				area.copy_data (s.area, s.area_lower, 0, count + 1)
			end
		ensure -- from READABLE_STRING_32
			not_shared_implementation: Current /= s implies not shared_with (s)
			initialized: same_string (s)
		end

	make_from_string_general (s: READABLE_STRING_GENERAL)
			-- Initialize from the characters of s.
		require -- from READABLE_STRING_32
			string_exists: s /= Void
		do
			if attached {READABLE_STRING_32} s as s32 then
				make_from_string (s32)
			else
				make (s.count)
				append_string_general (s)
			end
		ensure -- from READABLE_STRING_32
			not_shared_implementation: Current /= s
			initialized: same_string_general (s)
		end

	remake (n: INTEGER_32)
		obsolete "Use `make' instead. [2017-05-31]"
			-- Allocate space for at least n characters.
		require
			non_negative_size: n >= 0
		do
			make (n)
		ensure
			empty_string: count = 0
			area_allocated: capacity >= n
		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: CHARACTER_32; 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

	make_from_c_byte_array (a_byte_array: POINTER; a_character_count: INTEGER_32)
			-- Initialize from contents of a_byte_array for a length of a_character_count,
			-- given that each character is encoded in 4 bytes (little endian).
			-- ex: (char*) "a\000\000\000b\000\000\000c\000\000\000" for unicode STRING_32 "abc"
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			a_byte_array_exists: not a_byte_array.is_default_pointer
		do
			C_string_provider.set_shared_from_pointer_and_count (a_byte_array, 4 * a_character_count)
			create area.make_filled ('%U'.to_character_32, 4 * a_character_count + 1)
			count := a_character_count
			internal_hash_code := 0;
			C_string_provider.read_unicode_substring_into_character_32_area (area, 1, 4 * a_character_count)
		end

	make_from_c_pointer (c_string: POINTER)
		obsolete "Use `make_from_c'. [2017-05-31]"
			-- Create new instance from contents of c_string,
			-- a string created by some C function.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			c_string_exists: c_string /= default_pointer
		do
			make_from_c (c_string)
		end

	make_from_separate (other: separate READABLE_STRING_GENERAL)
			-- Initialize current string from other.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			other_not_void: other /= Void
		local
			i, nb: INTEGER_32
			l_area: like area
		do
			nb := other.count
			make (nb)
			from
				l_area := area
				i := 0
			until
				i = nb
			loop
				l_area.put (other.item (i + 1), i)
				i := i + 1
			end
			count := nb
		ensure -- from READABLE_STRING_32
			same_string: 
		end
	
feature -- Access

	area: SPECIAL [CHARACTER_32]
			-- Storage for characters

	at alias "@" (i: INTEGER_32): CHARACTER_32 assign put
			-- Character at position i
			-- Was declared in STRING_32 as synonym of item.
		require -- from  READABLE_STRING_32
			True
		require -- from TABLE
			valid_key: valid_index (i)
		require -- from TO_SPECIAL
			valid_index: valid_index (i)
		do
			Result := area.item (i - 1)
		end

	case_insensitive_hash_code: INTEGER_32
			-- Hash code value of the lower case version of Current.
			-- (from READABLE_STRING_GENERAL)
		local
			l_props: like Character_properties
			i, nb: INTEGER_32
		do
			Result := internal_case_insensitive_hash_code
			if Result = 0 then
				from
					i := 1
					nb := count
					l_props := Character_properties
				until
					i > nb
				loop
					Result := ((Result \\ 8388593) |<< 8) + l_props.to_lower (item (i)).code
					i := i + 1
				end
				internal_case_insensitive_hash_code := Result
			end
		ensure -- from READABLE_STRING_GENERAL
			consistent: Result = as_lower.case_insensitive_hash_code
		end

	code (i: INTEGER_32): NATURAL_32
			-- Character at position i
		require -- from READABLE_STRING_GENERAL
			valid_index: valid_index (i)
		do
			Result := area.item (i - 1).code.to_natural_32
		end

	False_constant: STRING_8 = "false"
			-- Constant string "false"
			-- (from READABLE_STRING_GENERAL)

	fuzzy_index (other: READABLE_STRING_GENERAL; start: INTEGER_32; fuzz: INTEGER_32): INTEGER_32
			-- Position of first occurrence of other at or after start
			-- with 0..fuzz mismatches between the string and other.
			-- 0 if there are no fuzzy matches
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_GENERAL
			other_exists: other /= Void
			other_not_empty: not other.is_empty
			start_large_enough: start >= 1
			start_small_enough: start <= count
			acceptable_fuzzy: fuzz <= other.count
		do
			Result := String_searcher.fuzzy_index (Current, other, start, count, fuzz)
		end

	generating_type: TYPE [detachable STRING_32]
			-- 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

	hash_code: INTEGER_32
			-- Hash code value
			-- (from READABLE_STRING_GENERAL)
		local
			i, nb: INTEGER_32
		do
			Result := internal_hash_code
			if Result = 0 then
				from
					i := 1
					nb := count
				until
					i > nb
				loop
					Result := ((Result \\ 8388593) |<< 8) + item (i).code
					i := i + 1
				end
				internal_hash_code := Result
			end
		ensure -- from HASHABLE
			good_hash_value: Result >= 0
		end

	index_of (c: CHARACTER_32; start_index: INTEGER_32): INTEGER_32
			-- Position of first occurrence of c at or after start_index;
			-- 0 if none.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_GENERAL
			start_large_enough: start_index >= 1
			start_small_enough: start_index <= count + 1
		local
			a: like area
			i, nb, l_lower_area: INTEGER_32
		do
			nb := count
			if start_index <= nb then
				from
					l_lower_area := area_lower
					i := start_index - 1 + l_lower_area
					nb := nb + l_lower_area
					a := area
				until
					i = nb or else a.item (i) = c
				loop
					i := i + 1
				end
				if i < nb then
					Result := i + 1 - l_lower_area
				end
			end
		ensure -- from READABLE_STRING_GENERAL
			valid_result: Result = 0 or (start_index <= Result and Result <= count)
			zero_if_absent: (Result = 0) = not substring (start_index, count).has (c)
			found_if_present: substring (start_index, count).has (c) implies item (Result) = c
			none_before: substring (start_index, count).has (c) implies not substring (start_index, Result - 1).has (c)
		end

	index_of_code (c: like code; start_index: INTEGER_32): INTEGER_32
			-- Position of first occurrence of c at or after start_index;
			-- 0 if none.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			start_large_enough: start_index >= 1
			start_small_enough: start_index <= count + 1
		local
			i, nb: INTEGER_32
		do
			nb := count
			if start_index <= nb then
				from
					i := start_index
				until
					i > nb or else code (i) = c
				loop
					i := i + 1
				end
				if i <= nb then
					Result := i
				end
			end
		ensure -- from READABLE_STRING_GENERAL
			valid_result: Result = 0 or (start_index <= Result and Result <= count)
			zero_if_absent: (Result = 0) = not substring (start_index, count).has_code (c)
			found_if_present: substring (start_index, count).has_code (c) implies code (Result) = c
			none_before: substring (start_index, count).has_code (c) implies not substring (start_index, Result - 1).has_code (c)
		end

	item alias "[]" (i: INTEGER_32): CHARACTER_32 assign put
			-- Character at position i
			-- Was declared in STRING_32 as synonym of at.
		require -- from READABLE_STRING_GENERAL
			valid_index: valid_index (i)
		require -- from READABLE_INDEXABLE
			valid_index: valid_index (i)
		require -- from TABLE
			valid_key: valid_index (i)
		require -- from TO_SPECIAL
			valid_index: valid_index (i)
		do
			Result := area.item (i - 1)
		end

	item_code (i: INTEGER_32): INTEGER_32
		obsolete "Due to potential truncation it is recommended to use `code (i)' instead. [2017-05-31]"
			-- Character at position i
		require -- from READABLE_STRING_32
			index_small_enough: i <= count
			index_large_enough: i > 0
		do
			Result := area.item (i - 1).natural_32_code.as_integer_32
		end

	last_index_of (c: CHARACTER_32; start_index_from_end: INTEGER_32): INTEGER_32
			-- Position of last occurrence of c.
			-- 0 if none.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_GENERAL
			start_index_small_enough: start_index_from_end <= count
			start_index_large_enough: start_index_from_end >= 1
		local
			a: like area
			i, l_lower_area: INTEGER_32
		do
			from
				l_lower_area := area_lower
				i := start_index_from_end - 1 + l_lower_area
				a := area
			until
				i < l_lower_area or else a.item (i) = c
			loop
				i := i - 1
			end
			Result := i + 1 - l_lower_area
		ensure -- from READABLE_STRING_GENERAL
			valid_result: 0 <= Result and Result <= start_index_from_end
			zero_if_absent: (Result = 0) = not substring (1, start_index_from_end).has (c)
			found_if_present: substring (1, start_index_from_end).has (c) implies item (Result) = c
			none_after: substring (1, start_index_from_end).has (c) implies not substring (Result + 1, start_index_from_end).has (c)
		end

	last_index_of_code (c: like code; start_index_from_end: INTEGER_32): INTEGER_32
			-- Position of last occurrence of c.
			-- 0 if none.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			start_index_small_enough: start_index_from_end <= count
			start_index_large_enough: start_index_from_end >= 1
		do
			from
				Result := start_index_from_end
			until
				Result <= 0 or else code (Result) = c
			loop
				Result := Result - 1
			end
		ensure -- from READABLE_STRING_GENERAL
			valid_result: 0 <= Result and Result <= start_index_from_end
			zero_if_absent: (Result = 0) = not substring (1, start_index_from_end).has_code (c)
			found_if_present: substring (1, start_index_from_end).has_code (c) implies code (Result) = c
			none_after: substring (1, start_index_from_end).has_code (c) implies not substring (Result + 1, start_index_from_end).has_code (c)
		end

	new_cursor: STRING_32_ITERATION_CURSOR
			-- Fresh cursor associated with current structure
			-- (from READABLE_STRING_32)
		require -- from  ITERABLE
			True
		do
			create Result.make (Current)
		ensure -- from ITERABLE
			result_attached: Result /= Void
		end

	shared_with (other: READABLE_STRING_32): BOOLEAN
			-- Does string share the text of other?
			-- (from READABLE_STRING_32)
		do
			Result := (other /= Void) and then (area = other.area)
		end

	string: STRING_32
			-- New STRING_32 having same character sequence as Current.
			-- (from READABLE_STRING_32)
		do
			create Result.make_from_string (Current)
		ensure -- from READABLE_STRING_32
			string_not_void: Result /= Void
			string_type: Result.same_type (create {STRING_32}.make_empty)
			first_item: count > 0 implies Result.item (1) = item (1)
			recurse: count > 1 implies Result.substring (2, count) ~ substring (2, count).string
		end

	string_representation: STRING_32
			-- Similar to string but only create a new object if Current is not of dynamic type STRING_32.
			-- (from READABLE_STRING_32)
		do
			if same_type (create {STRING_32}.make_empty) and then attached {STRING_32} Current as l_s32 then
				Result := l_s32
			else
				Result := string
			end
		ensure -- from READABLE_STRING_32
			result_not_void: Result /= Void
			correct_type: Result.same_type (create {STRING_32}.make_empty)
			first_item: count > 0 implies Result.item (1) = item (1)
			recurse: count > 1 implies Result.substring (2, count) ~ substring (2, count).string
		end

	substring_index (other: READABLE_STRING_GENERAL; start_index: INTEGER_32): INTEGER_32
			-- Index of first occurrence of other at or after start_index;
			-- 0 if none
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_GENERAL
			other_not_void: other /= Void
			valid_start_index: start_index >= 1 and start_index <= count + 1
		do
			Result := String_searcher.substring_index (Current, other, start_index, count)
		ensure -- from READABLE_STRING_GENERAL
			valid_result: Result = 0 or else (start_index <= Result and Result <= count - other.count + 1)
			zero_if_absent: (Result = 0) = not substring (start_index, count).has_substring (other)
			at_this_index: Result >= start_index implies other.same_string (substring (Result, Result + other.count - 1))
			none_before: Result > start_index implies not substring (start_index, Result + other.count - 2).has_substring (other)
		end

	substring_index_in_bounds (other: READABLE_STRING_GENERAL; start_pos, end_pos: INTEGER_32): INTEGER_32
			-- Position of first occurrence of other at or after start_pos
			-- and to or before end_pos;
			-- 0 if none.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_GENERAL
			other_nonvoid: other /= Void
			other_notempty: not other.is_empty
			start_pos_large_enough: start_pos >= 1
			start_pos_small_enough: start_pos <= count
			end_pos_large_enough: end_pos >= start_pos
			end_pos_small_enough: end_pos <= count
		do
			Result := String_searcher.substring_index (Current, other, start_pos, end_pos)
		ensure -- from READABLE_STRING_GENERAL
			correct_place: Result > 0 implies other.same_string (substring (Result, Result + other.count - 1))
		end

	True_constant: STRING_8 = "true"
			-- Constant string "true"
			-- (from READABLE_STRING_GENERAL)
	
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 characters allocated in Current
			-- (from READABLE_STRING_32)
		require -- from  READABLE_STRING_GENERAL
			True
		require -- from  BOUNDED
			True
		do
			Result := area.count - 1
		ensure -- from READABLE_STRING_GENERAL
			capacity_non_negative: Result >= 0
		ensure -- from BOUNDED
			capacity_non_negative: Result >= 0
		end

	count: INTEGER_32
			-- Actual number of characters making up the string.
			-- (from READABLE_STRING_32)

	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, count)
		ensure -- from READABLE_INDEXABLE
			not_void: Result /= Void
			empty_if_not_in_order: (Lower > count) implies Result.is_empty
			same_lower_if_not_empty: (Lower <= count) implies Result.lower = Lower
			same_upper_if_not_empty: (Lower <= count) implies Result.upper = count
		end

	Lower: INTEGER_32 = 1
			-- Minimum index.
			-- (from READABLE_STRING_32)

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

	occurrences (c: CHARACTER_32): INTEGER_32
			-- Number of times c appears in the string
			-- (from READABLE_STRING_32)
		require -- from  READABLE_STRING_GENERAL
			True
		require -- from  BAG
			True
		local
			i, nb: INTEGER_32
			a: SPECIAL [CHARACTER_32]
		do
			from
				i := area_lower
				nb := count + i
				a := area
			until
				i = nb
			loop
				if a.item (i) = c then
					Result := Result + 1
				end
				i := i + 1
			end
		ensure then -- from READABLE_STRING_GENERAL
			zero_if_empty: count = 0 implies Result = 0
			recurse_if_not_found_at_first_position: (count > 0 and then item (1) /= c) implies Result = substring (2, count).occurrences (c)
			recurse_if_found_at_first_position: (count > 0 and then item (1) = c) implies Result = 1 + substring (2, count).occurrences (c)
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
		ensure then -- from READABLE_STRING_32
			zero_if_empty: count = 0 implies Result = 0
			recurse_if_not_found_at_first_position: (count > 0 and then item (1) /= c) implies Result = substring (2, count).occurrences (c)
			recurse_if_found_at_first_position: (count > 0 and then item (1) = c) implies Result = 1 + substring (2, count).occurrences (c)
		end
	
feature {NONE} -- Measurement

	estimated_count_of (other: ITERABLE [CHARACTER_32]): INTEGER_32
			-- Estimated number of elements in other.
			-- (from CONTAINER)
		do
			if attached {FINITE [CHARACTER_32]} other as f then
				Result := f.count
			elseif attached {READABLE_INDEXABLE [CHARACTER_32]} 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

	ends_with_general (s: READABLE_STRING_GENERAL): BOOLEAN
			-- Does string finish with s?
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			argument_not_void: s /= Void
		local
			i, j: INTEGER_32
		do
			if Current = s then
				Result := True
			else
				i := s.count
				j := count
				if i <= j then
					from
						Result := True
					until
						i = 0
					loop
						if code (j) /= s.code (i) then
							Result := False
							i := 1
						end
						i := i - 1
						j := j - 1
					end
				end
			end
		ensure -- from READABLE_STRING_GENERAL
			definition: Result = s.same_string (substring (count - s.count + 1, count))
		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

	has_substring (other: READABLE_STRING_GENERAL): BOOLEAN
			-- Does Current contain other?
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			other_not_void: other /= Void
		do
			if other = Current then
				Result := True
			elseif other.count <= count then
				Result := substring_index (other, 1) > 0
			end
		ensure -- from READABLE_STRING_GENERAL
			false_if_too_small: count < other.count implies not Result
			true_if_initial: (count >= other.count and then other.same_string (substring (1, other.count))) implies Result
			recurse: (count >= other.count and then not other.same_string (substring (1, other.count))) implies (Result = substring (2, count).has_substring (other))
		end

	is_case_insensitive_equal_general (other: READABLE_STRING_GENERAL): BOOLEAN
			-- Is string made of same character sequence as other regardless of casing
			-- (possibly with a different capacity)?
			-- (from READABLE_STRING_GENERAL)
		local
			nb: INTEGER_32
		do
			if other = Current then
				Result := True
			else
				nb := count
				if nb = other.count then
					Result := nb = 0 or else same_caseless_characters_general (other, 1, nb, 1)
				end
			end
		ensure -- from READABLE_STRING_GENERAL
			symmetric: Result implies other.is_case_insensitive_equal (Current)
			consistent: attached {STRING_32} other as l_other implies (standard_is_equal (l_other) implies Result)
			valid_result: as_lower ~ other.as_lower implies Result
		end

	is_case_insensitive_equal (other: READABLE_STRING_32): BOOLEAN
			-- Is string made of same character sequence as other regardless of casing
			-- (possibly with a different capacity)?
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			other_not_void: other /= Void
		local
			nb: INTEGER_32
		do
			if other = Current then
				Result := True
			else
				nb := count
				if nb = other.count then
					Result := nb = 0 or else same_caseless_characters (other, 1, nb, 1)
				end
			end
		ensure -- from READABLE_STRING_32
			symmetric: Result implies other.is_case_insensitive_equal (Current)
			consistent: attached {STRING_32} other as l_other implies (standard_is_equal (l_other) implies Result)
			valid_result: as_lower.same_string (other.as_lower) implies Result
		end

	frozen is_deep_equal alias "≡≡≡" (other: STRING_32): 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: STRING_32): BOOLEAN
			-- Is string made of same character sequence as other
			-- (possibly with a different capacity)?
			-- (from READABLE_STRING_32)
		require -- from ANY
			other_not_void: other /= Void
		local
			nb: INTEGER_32
			l_hash, l_other_hash: like internal_hash_code
		do
			if other = Current then
				Result := True
			else
				nb := count
				if nb = other.count then
					l_hash := internal_hash_code
					l_other_hash := other.internal_hash_code
					if l_hash = 0 or else l_other_hash = 0 or else l_hash = l_other_hash then
						Result := area.same_items (other.area, other.area_lower, area_lower, nb)
					end
				end
			end
		ensure -- from ANY
			symmetric: Result implies other ~ Current
			consistent: standard_is_equal (other) implies Result
		ensure then -- from COMPARABLE
			trichotomy: Result = (not (Current < other) and not (other < Current))
		end

	is_greater alias ">" (other: STRING_32): BOOLEAN
			-- Is current object greater than other?
			-- (from COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		do
			Result := other < Current
		ensure then -- from COMPARABLE
			definition: Result = (other < Current)
		end

	is_greater_equal alias ">=" alias "≥" (other: STRING_32): BOOLEAN
			-- Is current object greater than or equal to other?
			-- (from COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		do
			Result := not (Current < other)
		ensure then -- from COMPARABLE
			definition: Result = (other <= Current)
		end

	is_less alias "<" (other: STRING_32): BOOLEAN
			-- Is string lexicographically lower than other?
			-- (from READABLE_STRING_32)
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		local
			other_count: INTEGER_32
			current_count: INTEGER_32
		do
			if other /= Current then
				other_count := other.count
				current_count := count
				if other_count = current_count then
					Result := str_strict_cmp (other.area, area, other.area_lower, area_lower, other_count) > 0
				else
					if current_count < other_count then
						Result := str_strict_cmp (other.area, area, other.area_lower, area_lower, current_count) >= 0
					else
						Result := str_strict_cmp (other.area, area, other.area_lower, area_lower, other_count) > 0
					end
				end
			end
		ensure then -- from COMPARABLE
			asymmetric: Result implies not (other < Current)
		end

	is_less_equal alias "<=" alias "≤" (other: STRING_32): BOOLEAN
			-- Is current object less than or equal to other?
			-- (from COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		do
			Result := not (other < Current)
		ensure then -- from COMPARABLE
			definition: Result = ((Current < other) or (Current ~ other))
		end

	max alias "∨" (other: STRING_32): STRING_32
			-- The greater of current object and other
			-- (from COMPARABLE)
		require -- from COMPARABLE
			other_exists: other /= Void
		do
			if Current >= other then
				Result := Current
			else
				Result := other
			end
		ensure -- from COMPARABLE
			current_if_not_smaller: Current >= other implies Result = Current
			other_if_smaller: Current < other implies Result = other
		end

	min alias "∧" (other: STRING_32): STRING_32
			-- The smaller of current object and other
			-- (from COMPARABLE)
		require -- from COMPARABLE
			other_exists: other /= Void
		do
			if Current <= other then
				Result := Current
			else
				Result := other
			end
		ensure -- from COMPARABLE
			current_if_not_greater: Current <= other implies Result = Current
			other_if_greater: Current > other implies Result = other
		end

	same_caseless_characters_general (other: READABLE_STRING_GENERAL; start_pos, end_pos, index_pos: INTEGER_32): BOOLEAN
			-- Are characters of other within bounds start_pos and end_pos
			-- caseless identical to characters of current string starting at index index_pos.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			other_not_void: other /= Void
			valid_start_pos: other.valid_index (start_pos)
			valid_end_pos: other.valid_index (end_pos)
			valid_bounds: (start_pos <= end_pos) or (start_pos = end_pos + 1)
			valid_index_pos: valid_index (index_pos)
		local
			i, j, nb: INTEGER_32
			l_prop: like Character_properties
			c1, c2: like item
		do
			nb := end_pos - start_pos + 1
			if nb <= count - index_pos + 1 then
				from
					l_prop := Character_properties
					Result := True
					i := index_pos
					j := start_pos
					nb := nb + i
				variant
					increasing_index: nb - i + 1
				until
					i = nb
				loop
					c1 := item (i)
					c2 := other.item (j)
					if c1 /= c2 and then l_prop.to_lower (c1) /= l_prop.to_lower (c2) then
						Result := False
						i := nb - 1
					end
					i := i + 1
					j := j + 1
				end
			end
		ensure -- from READABLE_STRING_GENERAL
			same_characters: Result = substring (index_pos, index_pos + end_pos - start_pos).is_case_insensitive_equal_general (other.substring (start_pos, end_pos))
		end

	same_caseless_characters (other: READABLE_STRING_32; start_pos, end_pos, index_pos: INTEGER_32): BOOLEAN
			-- Are characters of other within bounds start_pos and end_pos
			-- caseless identical to characters of current string starting at index index_pos.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			other_not_void: other /= Void
			valid_start_pos: other.valid_index (start_pos)
			valid_end_pos: other.valid_index (end_pos)
			valid_bounds: (start_pos <= end_pos) or (start_pos = end_pos + 1)
			valid_index_pos: valid_index (index_pos)
		local
			i, j, nb: INTEGER_32
			l_prop: like Character_properties
			l_area, l_other_area: like area
			c1, c2: CHARACTER_32
		do
			nb := end_pos - start_pos + 1
			if nb <= count - index_pos + 1 then
				from
					l_prop := Character_properties
					l_area := area
					l_other_area := other.area
					Result := True
					i := area_lower + index_pos - 1
					j := other.area_lower + start_pos - 1
					nb := nb + i
				variant
					increasing_index: nb - i + 1
				until
					i = nb
				loop
					c1 := l_area.item (i)
					c2 := l_other_area.item (j)
					if c1 /= c2 and then l_prop.to_lower (c1) /= l_prop.to_lower (c2) then
						Result := False
						i := nb - 1
					end
					i := i + 1
					j := j + 1
				end
			end
		ensure -- from READABLE_STRING_32
			same_characters: Result = substring (index_pos, index_pos + end_pos - start_pos).is_case_insensitive_equal (other.substring (start_pos, end_pos))
		end

	same_characters_general (other: READABLE_STRING_GENERAL; start_pos, end_pos, index_pos: INTEGER_32): BOOLEAN
			-- Are characters of other within bounds start_pos and end_pos
			-- identical to characters of current string starting at index index_pos.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			other_not_void: other /= Void
			valid_start_pos: other.valid_index (start_pos)
			valid_end_pos: other.valid_index (end_pos)
			valid_bounds: (start_pos <= end_pos) or (start_pos = end_pos + 1)
			valid_index_pos: valid_index (index_pos)
		local
			i, j, nb: INTEGER_32
		do
			nb := end_pos - start_pos + 1
			if nb <= count - index_pos + 1 then
				from
					Result := True
					i := index_pos
					j := start_pos
					nb := nb + i
				variant
					increasing_index: nb - i + 1
				until
					i = nb
				loop
					if item (i) /= other.item (j) then
						Result := False
						i := nb - 1
					end
					i := i + 1
					j := j + 1
				end
			end
		ensure -- from READABLE_STRING_GENERAL
			same_characters: Result = substring (index_pos, index_pos + end_pos - start_pos).same_string_general (other.substring (start_pos, end_pos))
		end

	same_characters (other: READABLE_STRING_32; start_pos, end_pos, index_pos: INTEGER_32): BOOLEAN
			-- Are characters of other within bounds start_pos and end_pos
			-- identical to characters of current string starting at index index_pos.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			other_not_void: other /= Void
			valid_start_pos: other.valid_index (start_pos)
			valid_end_pos: other.valid_index (end_pos)
			valid_bounds: (start_pos <= end_pos) or (start_pos = end_pos + 1)
			valid_index_pos: valid_index (index_pos)
		local
			nb: INTEGER_32
		do
			nb := end_pos - start_pos + 1
			if nb <= count - index_pos + 1 then
				Result := area.same_items (other.area, other.area_lower + start_pos - 1, area_lower + index_pos - 1, nb)
			end
		ensure -- from READABLE_STRING_32
			same_characters: Result = substring (index_pos, index_pos + end_pos - start_pos).same_string (other.substring (start_pos, end_pos))
		end

	same_string (other: READABLE_STRING_32): BOOLEAN
			-- Do Current and other have same character sequence?
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			other_not_void: other /= Void
		local
			nb: INTEGER_32
		do
			if other = Current then
				Result := True
			else
				nb := count
				if nb = other.count then
					Result := nb = 0 or else same_characters (other, 1, nb, 1)
				end
			end
		ensure -- from READABLE_STRING_32
			definition: Result = (string ~ other.string)
		end

	same_string_general (other: READABLE_STRING_GENERAL): BOOLEAN
			-- Does other represent the same string as Current?
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			other_not_void: other /= Void
		local
			nb: INTEGER_32
		do
			if other = Current then
				Result := True
			else
				nb := count
				if nb = other.count then
					Result := nb = 0 or else same_characters_general (other, 1, nb, 1)
				end
			end
		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: STRING_32): 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

	starts_with_general (s: READABLE_STRING_GENERAL): BOOLEAN
			-- Does string begin with s?
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			argument_not_void: s /= Void
		local
			i: INTEGER_32
		do
			if Current = s then
				Result := True
			else
				i := s.count
				if i <= count then
					from
						Result := True
					until
						i = 0
					loop
						if code (i) /= s.code (i) then
							Result := False
							i := 1
						end
						i := i - 1
					end
				end
			end
		ensure -- from READABLE_STRING_GENERAL
			definition: Result = s.same_string (substring (1, s.count))
		end

	three_way_comparison alias "⋚" (other: STRING_32): INTEGER_32
			-- If current object equal to other, 0;
			-- if smaller, -1; if greater, 1
			-- (from COMPARABLE)
		require -- from COMPARABLE
			other_exists: other /= Void
		do
			if Current < other then
				Result := -1
			elseif other < Current then
				Result := 1
			end
		ensure -- from COMPARABLE
			equal_zero: (Result = 0) = (Current ~ other)
			smaller_negative: (Result = -1) = (Current < other)
			greater_positive: (Result = 1) = (Current > other)
		end
	
feature -- Status report

	Changeable_comparison_criterion: BOOLEAN = False
			-- May object_comparison be changed?
			-- (Answer: yes by default.)

	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

	ends_with (s: READABLE_STRING_32): BOOLEAN
			-- Does string finish with s?
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			argument_not_void: s /= Void
		local
			i, j, nb: INTEGER_32
			l_area, l_s_area: like area
		do
			if Current = s then
				Result := True
			else
				i := s.count
				j := count
				if i <= j then
					from
						l_area := area
						l_s_area := s.area
						j := area_upper + 1
						i := s.area_upper + 1
						nb := s.area_lower
						Result := True
					until
						i = nb
					loop
						i := i - 1
						j := j - 1
						if l_area.item (j) /= l_s_area.item (i) then
							Result := False
							i := nb
						end
					end
				end
			end
		ensure -- from READABLE_STRING_32
			definition: Result = s.same_string (substring (count - s.count + 1, count))
		end

	Extendible: BOOLEAN = True
			-- May new items be added? (Answer: yes.)

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

	has (c: CHARACTER_32): BOOLEAN
			-- Does string include c?
			-- (from READABLE_STRING_32)
		require -- from  READABLE_STRING_GENERAL
			True
		require -- from  CONTAINER
			True
		local
			i, nb: INTEGER_32
			l_area: like area
		do
			nb := count
			if nb > 0 then
				from
					i := area_lower
					l_area := area
					nb := nb + i
				until
					i = nb or else l_area.item (i) = c
				loop
					i := i + 1
				end
				Result := i < nb
			end
		ensure then -- from READABLE_STRING_GENERAL
			false_if_empty: count = 0 implies not Result
			true_if_first: count > 0 and then item (1) = c implies Result
			recurse: (count > 0 and then item (1) /= c) implies (Result = substring (2, count).has (c))
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty
		end

	has_code (c: like code): BOOLEAN
			-- Does string include c?
			-- (from READABLE_STRING_GENERAL)
		local
			i, nb: INTEGER_32
		do
			nb := count
			if nb > 0 then
				from
					i := 1
				until
					i > nb or else (code (i) = c)
				loop
					i := i + 1
				end
				Result := i <= nb
			end
		ensure then -- from READABLE_STRING_GENERAL
			false_if_empty: count = 0 implies not Result
			true_if_first: count > 0 and then code (1) = c implies Result
			recurse: (count > 0 and then code (1) /= c) implies (Result = substring (2, count).has_code (c))
		end

	is_boolean: BOOLEAN
			-- Does Current represent a BOOLEAN?
			-- (from READABLE_STRING_32)
		require -- from  READABLE_STRING_GENERAL
			True
		local
			nb: INTEGER_32
		do
			nb := count
			if nb = 4 then
				Result := is_case_insensitive_equal_general (True_constant)
			elseif nb = 5 then
				Result := is_case_insensitive_equal_general (False_constant)
			end
		ensure -- from READABLE_STRING_GENERAL
			is_boolean: Result = (True_constant.same_string_general (as_lower) or False_constant.same_string_general (as_lower))
		end

	is_double: BOOLEAN
			-- Does Current represent a REAL_64?
			-- Was declared in READABLE_STRING_GENERAL as synonym of is_real_64.
			-- (from READABLE_STRING_GENERAL)
		local
			l_convertor: like Ctor_convertor
		do
			l_convertor := Ctor_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_double)
			Result := l_convertor.is_integral_double
		end

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

	is_hashable: BOOLEAN
			-- May current object be hashed?
			-- (True by default.)
			-- (from HASHABLE)
		do
			Result := True
		end

	is_immutable: BOOLEAN
			-- Can the character sequence of Current be not changed?
			-- (from READABLE_STRING_GENERAL)
		do
			Result := False
		end

	is_inserted (v: CHARACTER_32): 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

	is_integer: BOOLEAN
			-- Does Current represent an INTEGER_32?
			-- Was declared in READABLE_STRING_GENERAL as synonym of is_integer_32.
			-- (from READABLE_STRING_GENERAL)
		do
			Result := is_valid_integer_or_natural ({NUMERIC_INFORMATION}.type_integer_32)
		end

	is_integer_16: BOOLEAN
			-- Does Current represent an INTEGER_16?
			-- (from READABLE_STRING_GENERAL)
		do
			Result := is_valid_integer_or_natural ({NUMERIC_INFORMATION}.type_integer_16)
		end

	is_integer_32: BOOLEAN
			-- Does Current represent an INTEGER_32?
			-- Was declared in READABLE_STRING_GENERAL as synonym of is_integer.
			-- (from READABLE_STRING_GENERAL)
		do
			Result := is_valid_integer_or_natural ({NUMERIC_INFORMATION}.type_integer_32)
		end

	is_integer_64: BOOLEAN
			-- Does Current represent an INTEGER_64?
			-- (from READABLE_STRING_GENERAL)
		do
			Result := is_valid_integer_or_natural ({NUMERIC_INFORMATION}.type_integer_64)
		end

	is_integer_8: BOOLEAN
			-- Does Current represent an INTEGER_8?
			-- (from READABLE_STRING_GENERAL)
		do
			Result := is_valid_integer_or_natural ({NUMERIC_INFORMATION}.type_integer_8)
		end

	is_natural: BOOLEAN
			-- Does Current represent a NATURAL_32?
			-- Was declared in READABLE_STRING_GENERAL as synonym of is_natural_32.
			-- (from READABLE_STRING_GENERAL)
		do
			Result := is_valid_integer_or_natural ({NUMERIC_INFORMATION}.type_natural_32)
		end

	is_natural_16: BOOLEAN
			-- Does Current represent a NATURAL_16?
			-- (from READABLE_STRING_GENERAL)
		do
			Result := is_valid_integer_or_natural ({NUMERIC_INFORMATION}.type_natural_16)
		end

	is_natural_32: BOOLEAN
			-- Does Current represent a NATURAL_32?
			-- Was declared in READABLE_STRING_GENERAL as synonym of is_natural.
			-- (from READABLE_STRING_GENERAL)
		do
			Result := is_valid_integer_or_natural ({NUMERIC_INFORMATION}.type_natural_32)
		end

	is_natural_64: BOOLEAN
			-- Does Current represent a NATURAL_64?
			-- (from READABLE_STRING_GENERAL)
		do
			Result := is_valid_integer_or_natural ({NUMERIC_INFORMATION}.type_natural_64)
		end

	is_natural_8: BOOLEAN
			-- Does Current represent a NATURAL_8?
			-- (from READABLE_STRING_GENERAL)
		do
			Result := is_valid_integer_or_natural ({NUMERIC_INFORMATION}.type_natural_8)
		end

	is_number_sequence: BOOLEAN
			-- Does Current represent a number sequence?
			-- (from READABLE_STRING_GENERAL)
		do
			Result := is_valid_integer_or_natural ({NUMERIC_INFORMATION}.type_no_limitation)
		end

	is_real: BOOLEAN
			-- Does Current represent a REAL_32?
			-- Was declared in READABLE_STRING_GENERAL as synonym of is_real_32.
			-- (from READABLE_STRING_GENERAL)
		local
			l_convertor: like Ctor_convertor
		do
			l_convertor := Ctor_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_real)
			Result := l_convertor.is_integral_real
		end

	is_real_32: BOOLEAN
			-- Does Current represent a REAL_32?
			-- Was declared in READABLE_STRING_GENERAL as synonym of is_real.
			-- (from READABLE_STRING_GENERAL)
		local
			l_convertor: like Ctor_convertor
		do
			l_convertor := Ctor_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_real)
			Result := l_convertor.is_integral_real
		end

	is_real_64: BOOLEAN
			-- Does Current represent a REAL_64?
			-- Was declared in READABLE_STRING_GENERAL as synonym of is_double.
			-- (from READABLE_STRING_GENERAL)
		local
			l_convertor: like Ctor_convertor
		do
			l_convertor := Ctor_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_double)
			Result := l_convertor.is_integral_double
		end

	is_real_sequence: BOOLEAN
			-- Does Current represent a real sequence?
			-- (from READABLE_STRING_GENERAL)
		local
			l_convertor: like Ctor_convertor
		do
			l_convertor := Ctor_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_no_limitation)
			Result := l_convertor.is_integral_double
		end

	Is_string_32: BOOLEAN = True
			-- Is Current a sequence of CHARACTER_32?
			-- (from READABLE_STRING_32)

	Is_string_8: BOOLEAN = False
			-- Is Current a sequence of CHARACTER_8?
			-- (from READABLE_STRING_32)

	is_substring_whitespace (start_index, end_index: INTEGER_32): BOOLEAN
			-- Is substring between start_index and end_index containing only whitespace characters?
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_GENERAL
			start_index_big_enough: 1 <= start_index
			end_index_small_enough: end_index <= count
			consistent_indexes: start_index - 1 <= end_index
		local
			i, n: INTEGER_32
			l_prop: like Character_properties
			l_area: like area
		do
			from
				l_area := area
				i := area_lower + start_index - 1
				n := area_lower + end_index - 1
				l_prop := Character_properties
			until
				i > n or not l_prop.is_space (l_area.item (i))
			loop
				i := i + 1
			end
			Result := i > n
		end

	is_valid_as_string_8: BOOLEAN
			-- Is Current convertible to a sequence of CHARACTER_8 without information loss?
			-- (from READABLE_STRING_32)
		require -- from  READABLE_STRING_GENERAL
			True
		local
			i, nb: INTEGER_32
			l_area: like area
		do
			from
				Result := True
				i := area_lower
				nb := count + i
				l_area := area
			until
				i = nb or not Result
			loop
				Result := l_area.item (i).code <= {CHARACTER_8}.max_value
				i := i + 1
			end
		end

	is_whitespace: BOOLEAN
			-- Is structure containing only whitespace characters?
			-- (from READABLE_STRING_GENERAL)
		do
			Result := is_substring_whitespace (1, count)
		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: yes.)
			-- (from DYNAMIC_TABLE)
		require -- from  COLLECTION
			True
		do
			Result := True
		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

	starts_with (s: READABLE_STRING_32): BOOLEAN
			-- Does string begin with s?
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			argument_not_void: s /= Void
		local
			i, j, nb: INTEGER_32
			l_area, l_s_area: like area
		do
			if Current = s then
				Result := True
			else
				i := s.count
				if i <= count then
					from
						l_area := area
						l_s_area := s.area
						j := area_lower + i
						i := s.area_upper + 1
						nb := s.area_lower
						Result := True
					until
						i = nb
					loop
						i := i - 1
						j := j - 1
						if l_area.item (j) /= l_s_area.item (i) then
							Result := False
							i := nb
						end
					end
				end
			end
		ensure -- from READABLE_STRING_32
			definition: Result = s.same_string (substring (1, s.count))
		end

	valid_code (v: NATURAL_32): BOOLEAN
			-- Is v a valid code for a CHARACTER_32?
			-- (from READABLE_STRING_32)
		require -- from  READABLE_STRING_GENERAL
			True
		do
			Result := True
		end

	valid_index (i: INTEGER_32): BOOLEAN
			-- Is i within the bounds of the string?
			-- (from READABLE_STRING_GENERAL)
		require -- from  READABLE_INDEXABLE
			True
		require -- from  TABLE
			True
		require -- from  TO_SPECIAL
			True
		do
			Result := (i > 0) and (i <= count)
		ensure -- from READABLE_INDEXABLE
			only_if_in_index_set: Result implies (Lower <= i and i <= count)
		ensure -- from READABLE_STRING_GENERAL
			definition: Result = (1 <= i and i <= count)
		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

	adjust
			-- Remove leading and/or trailing whitespace.
			-- (from STRING_GENERAL)
		do
			left_adjust
			right_adjust
		ensure -- from STRING_GENERAL
			valid_count: count <= old count
			new_count_left: not is_empty implies not item (1).is_space
			new_count_right: not is_empty implies not item (count).is_space
			kept: Elks_checking implies (old twin).has_substring (Current)
			only_spaces_removed_before: Elks_checking implies (old twin).is_substring_whitespace (1, (old twin).substring_index (Current, 1) - 1)
			only_spaces_removed_after: Elks_checking implies (old twin).is_substring_whitespace ((old twin).substring_index (Current, 1) + count, old count)
		end

	append (s: READABLE_STRING_32)
			-- Append characters of s at end.
		require
			argument_not_void: s /= Void
		local
			l_count, l_s_count, l_new_size: INTEGER_32
		do
			l_s_count := s.count
			if l_s_count > 0 then
				l_count := count
				l_new_size := l_s_count + l_count
				if l_new_size > capacity then
					resize (l_new_size + additional_space)
				end;
				area.copy_data (s.area, s.area_lower, l_count, l_s_count)
				count := l_new_size
				reset_hash_codes
			end
		ensure
			new_count: count = old count + old s.count
			appended: Elks_checking implies same_string (old (Current + s))
		end

	append_boolean (b: BOOLEAN)
			-- Append the string representation of b at end.
		do
			append_string_general (b.out)
		end

	append_character (c: CHARACTER_32)
			-- Append c at end.
			-- Was declared in STRING_32 as synonym of extend.
		local
			current_count: INTEGER_32
		do
			current_count := count
			if current_count = capacity then
				resize (current_count + additional_space)
			end;
			area.put (c, current_count)
			count := current_count + 1
			reset_hash_codes
		ensure then
			item_inserted: item (count) = c
			new_count: count = old count + 1
			stable_before: Elks_checking implies substring (1, count - 1) ~ (old twin)
		end

	append_code (c: like code)
			-- Append c at end.
			-- (from STRING_GENERAL)
		require -- from STRING_GENERAL
			valid_code: valid_code (c)
		local
			current_count: INTEGER_32
		do
			current_count := count + 1
			if current_count > capacity then
				resize (current_count)
			end
			set_count (current_count)
			put_code (c, current_count)
		ensure then -- from STRING_GENERAL
			item_inserted: code (count) = c
			new_count: count = old count + 1
			stable_before: Elks_checking implies substring (1, count - 1) ~ (old twin)
		end

	append_double (d: REAL_64)
			-- Append the string representation of d at end.
		do
			append_string_general (d.out)
		end

	append_integer (i: INTEGER_32)
			-- Append the string representation of i at end.
		local
			l_value: INTEGER_32
			l_starting_index, l_ending_index: INTEGER_32
			l_temp: CHARACTER_32
			l_area: like area
		do
			if i = 0 then
				append_character ('0'.to_character_32)
			else
				from
					l_starting_index := count
					if i < 0 then
						append_character ('-'.to_character_32)
						l_starting_index := l_starting_index + 1
						if i = {INTEGER_32}.min_value then
							append_character ('8'.to_character_32)
							l_value := - (i // 10)
						else
							l_value := - i
						end
					else
						l_value := i
					end
				until
					l_value = 0
				loop
					append_character ((l_value \\ 10 + 48).to_character_32)
					l_value := l_value // 10
				end
				from
					l_ending_index := count - 1
					l_area := area
				until
					l_starting_index >= l_ending_index
				loop
					l_temp := l_area.item (l_starting_index);
					l_area.put (l_area.item (l_ending_index), l_starting_index);
					l_area.put (l_temp, l_ending_index)
					l_ending_index := l_ending_index - 1
					l_starting_index := l_starting_index + 1
				end
			end
		end

	append_integer_16 (i: INTEGER_16)
			-- Append the string representation of i at end.
		local
			l_value: INTEGER_16
			l_starting_index, l_ending_index: INTEGER_32
			l_temp: CHARACTER_32
			l_area: like area
		do
			if i = 0 then
				append_character ('0'.to_character_32)
			else
				from
					l_starting_index := count
					if i < 0 then
						append_character ('-'.to_character_32)
						l_starting_index := l_starting_index + 1
						if i = {INTEGER_16}.min_value then
							append_character ('8'.to_character_32)
							l_value := - (i // 10)
						else
							l_value := - i
						end
					else
						l_value := i
					end
				until
					l_value = 0
				loop
					append_character ((l_value \\ 10 + 48).to_character_32)
					l_value := l_value // 10
				end
				from
					l_ending_index := count - 1
					l_area := area
				until
					l_starting_index >= l_ending_index
				loop
					l_temp := l_area.item (l_starting_index);
					l_area.put (l_area.item (l_ending_index), l_starting_index);
					l_area.put (l_temp, l_ending_index)
					l_ending_index := l_ending_index - 1
					l_starting_index := l_starting_index + 1
				end
			end
		end

	append_integer_64 (i: INTEGER_64)
			-- Append the string representation of i at end.
		local
			l_value: INTEGER_64
			l_starting_index, l_ending_index: INTEGER_32
			l_temp: CHARACTER_32
			l_area: like area
		do
			if i = 0 then
				append_character ('0'.to_character_32)
			else
				from
					l_starting_index := count
					if i < 0 then
						append_character ('-'.to_character_32)
						l_starting_index := l_starting_index + 1
						if i = {INTEGER_64}.min_value then
							append_character ('8'.to_character_32)
							l_value := - (i // 10)
						else
							l_value := - i
						end
					else
						l_value := i
					end
				until
					l_value = 0
				loop
					append_character ((l_value \\ 10 + 48).to_character_32)
					l_value := l_value // 10
				end
				from
					l_ending_index := count - 1
					l_area := area
				until
					l_starting_index >= l_ending_index
				loop
					l_temp := l_area.item (l_starting_index);
					l_area.put (l_area.item (l_ending_index), l_starting_index);
					l_area.put (l_temp, l_ending_index)
					l_ending_index := l_ending_index - 1
					l_starting_index := l_starting_index + 1
				end
			end
		end

	append_integer_8 (i: INTEGER_8)
			-- Append the string representation of i at end.
		local
			l_value: INTEGER_8
			l_starting_index, l_ending_index: INTEGER_32
			l_temp: CHARACTER_32
			l_area: like area
		do
			if i = 0 then
				append_character ('0'.to_character_32)
			else
				from
					l_starting_index := count
					if i < 0 then
						append_character ('-'.to_character_32)
						l_starting_index := l_starting_index + 1
						if i = {INTEGER_8}.min_value then
							append_character ('8'.to_character_32)
							l_value := - (i // 10)
						else
							l_value := - i
						end
					else
						l_value := i
					end
				until
					l_value = 0
				loop
					append_character ((l_value \\ 10 + 48).to_character_32)
					l_value := l_value // 10
				end
				from
					l_ending_index := count - 1
					l_area := area
				until
					l_starting_index >= l_ending_index
				loop
					l_temp := l_area.item (l_starting_index);
					l_area.put (l_area.item (l_ending_index), l_starting_index);
					l_area.put (l_temp, l_ending_index)
					l_ending_index := l_ending_index - 1
					l_starting_index := l_starting_index + 1
				end
			end
		end

	append_natural_16 (i: NATURAL_16)
			-- Append the string representation of i at end.
		local
			l_value: NATURAL_16
			l_starting_index, l_ending_index: INTEGER_32
			l_temp: CHARACTER_32
			l_area: like area
		do
			if i = 0 then
				append_character ('0'.to_character_32)
			else
				from
					l_starting_index := count
					l_value := i
				until
					l_value = 0
				loop
					append_character ((l_value \\ 10 + 48).to_character_32)
					l_value := l_value // 10
				end
				from
					l_ending_index := count - 1
					l_area := area
				until
					l_starting_index >= l_ending_index
				loop
					l_temp := l_area.item (l_starting_index);
					l_area.put (l_area.item (l_ending_index), l_starting_index);
					l_area.put (l_temp, l_ending_index)
					l_ending_index := l_ending_index - 1
					l_starting_index := l_starting_index + 1
				end
			end
		end

	append_natural_32 (i: NATURAL_32)
			-- Append the string representation of i at end.
		local
			l_value: NATURAL_32
			l_starting_index, l_ending_index: INTEGER_32
			l_temp: CHARACTER_32
			l_area: like area
		do
			if i = 0 then
				append_character ('0'.to_character_32)
			else
				from
					l_starting_index := count
					l_value := i
				until
					l_value = 0
				loop
					append_character ((l_value \\ 10 + 48).to_character_32)
					l_value := l_value // 10
				end
				from
					l_ending_index := count - 1
					l_area := area
				until
					l_starting_index >= l_ending_index
				loop
					l_temp := l_area.item (l_starting_index);
					l_area.put (l_area.item (l_ending_index), l_starting_index);
					l_area.put (l_temp, l_ending_index)
					l_ending_index := l_ending_index - 1
					l_starting_index := l_starting_index + 1
				end
			end
		end

	append_natural_64 (i: NATURAL_64)
			-- Append the string representation of i at end.
		local
			l_value: NATURAL_64
			l_starting_index, l_ending_index: INTEGER_32
			l_temp: CHARACTER_32
			l_area: like area
		do
			if i = 0 then
				append_character ('0'.to_character_32)
			else
				from
					l_starting_index := count
					l_value := i
				until
					l_value = 0
				loop
					append_character ((l_value \\ 10 + 48).to_character_32)
					l_value := l_value // 10
				end
				from
					l_ending_index := count - 1
					l_area := area
				until
					l_starting_index >= l_ending_index
				loop
					l_temp := l_area.item (l_starting_index);
					l_area.put (l_area.item (l_ending_index), l_starting_index);
					l_area.put (l_temp, l_ending_index)
					l_ending_index := l_ending_index - 1
					l_starting_index := l_starting_index + 1
				end
			end
		end

	append_natural_8 (i: NATURAL_8)
			-- Append the string representation of i at end.
		local
			l_value: NATURAL_8
			l_starting_index, l_ending_index: INTEGER_32
			l_temp: CHARACTER_32
			l_area: like area
		do
			if i = 0 then
				append_character ('0'.to_character_32)
			else
				from
					l_starting_index := count
					l_value := i
				until
					l_value = 0
				loop
					append_character ((l_value \\ 10 + 48).to_character_32)
					l_value := l_value // 10
				end
				from
					l_ending_index := count - 1
					l_area := area
				until
					l_starting_index >= l_ending_index
				loop
					l_temp := l_area.item (l_starting_index);
					l_area.put (l_area.item (l_ending_index), l_starting_index);
					l_area.put (l_temp, l_ending_index)
					l_ending_index := l_ending_index - 1
					l_starting_index := l_starting_index + 1
				end
			end
		end

	append_real (r: REAL_32)
			-- Append the string representation of r at end.
		do
			append_string_general (r.out)
		end

	append_string (s: detachable READABLE_STRING_32)
			-- Append a copy of s, if not void, at end.
		do
			if s /= Void then
				append (s)
			end
		ensure
			appended: s /= Void implies (Elks_checking implies Current ~ (old twin + old s.twin))
		end

	append_string_general (s: READABLE_STRING_GENERAL)
			-- Append characters of s at end.
		require -- from STRING_GENERAL
			argument_not_void: s /= Void
			compatible_strings: Is_string_8 implies s.is_valid_as_string_8
		do
			if attached {READABLE_STRING_32} s as l_s32 then
				append (l_s32)
			else
				Precursor {STRING_GENERAL} (s)
			end
		ensure -- from STRING_GENERAL
			new_count: count = old count + old s.count
			appended: Elks_checking implies same_string_general (old (to_string_32 + s.as_string_32))
		end

	append_substring_general (s: READABLE_STRING_GENERAL; start_index, end_index: INTEGER_32)
			-- Append characters of s.substring (start_index, end_index) at end.
			-- (from STRING_GENERAL)
		require -- from STRING_GENERAL
			argument_not_void: s /= Void
			compatible_strings: Is_string_8 implies s.is_valid_as_string_8
			start_index_valid: start_index >= 1
			end_index_valid: end_index <= s.count
			valid_bounds: start_index <= end_index + 1
		local
			l_s_count, l_new_size: INTEGER_32
			i: INTEGER_32
		do
			l_s_count := end_index - start_index + 1
			if l_s_count > 0 then
				l_new_size := l_s_count + count
				if l_new_size > capacity then
					resize (l_new_size)
				end
				from
					i := start_index
				until
					i > end_index
				loop
					append_code (s.code (i))
					i := i + 1
				end
				set_count (l_new_size)
				reset_hash_codes
			end
		ensure -- from STRING_GENERAL
			new_count: count = old count + end_index - start_index + 1
			appended: Elks_checking implies same_string_general (old (to_string_32 + s.substring (start_index, end_index).as_string_32))
		end

	append_substring (s: READABLE_STRING_32; start_index, end_index: INTEGER_32)
			-- Append characters of s.substring (start_index, end_index) at end.
		require
			argument_not_void: s /= Void
			start_index_valid: start_index >= 1
			end_index_valid: end_index <= s.count
			valid_bounds: start_index <= end_index + 1
		local
			l_count, l_s_count, l_new_size: INTEGER_32
		do
			l_s_count := end_index - start_index + 1
			if l_s_count > 0 then
				l_count := count
				l_new_size := l_s_count + l_count
				if l_new_size > capacity then
					resize (l_new_size + additional_space)
				end;
				area.copy_data (s.area, s.area_lower + start_index - 1, l_count, l_s_count)
				count := l_new_size
				reset_hash_codes
			end
		ensure
			new_count: count = old count + (end_index - start_index + 1)
			appended: Elks_checking implies same_string (old (Current + s.substring (start_index, end_index)))
		end

	extend (c: CHARACTER_32)
			-- Append c at end.
			-- Was declared in STRING_32 as synonym of append_character.
		require -- from COLLECTION
			extendible: Extendible
		local
			current_count: INTEGER_32
		do
			current_count := count
			if current_count = capacity then
				resize (current_count + additional_space)
			end;
			area.put (c, current_count)
			count := current_count + 1
			reset_hash_codes
		ensure -- from COLLECTION
			item_inserted: is_inserted (c)
		ensure then
			item_inserted: item (count) = c
			new_count: count = old count + 1
			stable_before: Elks_checking implies substring (1, count - 1) ~ (old twin)
		end

	fill (other: CONTAINER [CHARACTER_32])
			-- 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 [CHARACTER_32]
		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_blank
			-- Fill with capacity blank characters.
		do
			fill_character (' '.to_character_32)
		ensure
			filled: full
			same_size: (count = capacity) and (capacity = old capacity)
		end

	fill_character (c: CHARACTER_32)
			-- Fill with capacity characters all equal to c.
			-- (from READABLE_STRING_32)
		local
			l_cap: like capacity
		do
			l_cap := capacity
			if l_cap /= 0 then
				area.fill_with (c, 0, l_cap - 1)
				count := l_cap
				internal_hash_code := 0
			end
		ensure -- from READABLE_STRING_32
			filled: count = capacity
			same_size: capacity = old capacity
		end

	fill_with (c: CHARACTER_32)
			-- Replace every character with c.
		local
			l_count: INTEGER_32
		do
			l_count := count
			if l_count /= 0 then
				area.fill_with (c, 0, l_count - 1)
				reset_hash_codes
			end
		ensure
			same_count: (count = old count) and (capacity = old capacity)
			filled: Elks_checking implies occurrences (c) = count
		end

	insert (s: READABLE_STRING_32; i: INTEGER_32)
		obsolete "ELKS 2001: use `insert_string' instead. [2017-05-31]"
			-- Add s to left of position i in current string.
		require
			string_exists: s /= Void
			index_small_enough: i <= count + 1
			index_large_enough: i > 0
		do
			insert_string (s, i)
		ensure
			inserted: Elks_checking implies (Current ~ (old substring (1, i - 1) + old (s.twin) + old substring (i, count)))
		end

	insert_character (c: CHARACTER_32; i: INTEGER_32)
			-- Insert c at index i, shifting characters between ranks
			-- i and count rightwards.
		require
			valid_insertion_index: 1 <= i and i <= count + 1
		local
			pos, new_size: INTEGER_32
			l_area: like area
		do
			new_size := 1 + count
			if new_size > capacity then
				resize (new_size + additional_space)
			end
			pos := i - 1
			l_area := area;
			l_area.overlapping_move (pos, pos + 1, count - pos);
			l_area.put (c, pos)
			count := new_size
			reset_hash_codes
		ensure
			one_more_character: count = old count + 1
			inserted: item (i) = c
			stable_before_i: Elks_checking implies substring (1, i - 1) ~ (old substring (1, i - 1))
			stable_after_i: Elks_checking implies substring (i + 1, count) ~ (old substring (i, count))
		end

	insert_string (s: READABLE_STRING_32; i: INTEGER_32)
			-- Insert s at index i, shifting characters between ranks
			-- i and count rightwards.
		require
			string_exists: s /= Void
			valid_insertion_index: 1 <= i and i <= count + 1
		local
			pos, new_size: INTEGER_32
			l_s_count: INTEGER_32
			l_area: like area
		do
			l_s_count := s.count
			if l_s_count /= 0 then
				new_size := l_s_count + count
				if new_size > capacity then
					resize (new_size + additional_space)
				end
				l_area := area
				pos := i - 1;
				l_area.overlapping_move (pos, pos + l_s_count, count - pos);
				l_area.copy_data (s.area, s.area_lower, pos, l_s_count)
				count := new_size
				reset_hash_codes
			end
		ensure
			inserted: Elks_checking implies (Current ~ (old substring (1, i - 1) + old (s.twin) + old substring (i, count)))
		end

	keep_head (n: INTEGER_32)
			-- Remove all characters except for the first n;
			-- do nothing if n >= count.
		require -- from STRING_GENERAL
			non_negative_argument: n >= 0
		do
			if n < count then
				count := n
				reset_hash_codes
			end
		ensure -- from STRING_GENERAL
			new_count: count = n.min (old count)
			kept: Elks_checking implies Current ~ (old substring (1, n.min (count)))
		end

	keep_tail (n: INTEGER_32)
			-- Remove all characters except for the last n;
			-- do nothing if n >= count.
		require -- from STRING_GENERAL
			non_negative_argument: n >= 0
		local
			nb: like count
		do
			nb := count
			if n < nb then
				area.overlapping_move (nb - n, 0, n)
				count := n
				reset_hash_codes
			end
		ensure -- from STRING_GENERAL
			new_count: count = n.min (old count)
			kept: Elks_checking implies Current ~ (old substring (count - n.min (count) + 1, count))
		end

	left_adjust
			-- Remove leading whitespace.
		local
			nb, nb_space: INTEGER_32
			l_area: like area
			l_prop: like Character_properties
		do
			l_prop := Character_properties
			from
				nb := count - 1
				l_area := area
			until
				nb_space > nb or else not l_prop.is_space (l_area.item (nb_space))
			loop
				nb_space := nb_space + 1
			end
			if nb_space > 0 then
				nb := nb + 1 - nb_space;
				l_area.overlapping_move (nb_space, 0, nb)
				count := nb
				reset_hash_codes
			end
		ensure -- from STRING_GENERAL
			valid_count: count <= old count
			new_count: not is_empty implies not item (1).is_space
			kept: Elks_checking implies Current ~ (old twin).substring (old count - count + 1, old count)
			only_spaces_removed_before: Elks_checking implies (old twin).is_substring_whitespace (1, (old twin).substring_index (Current, 1) - 1)
		end

	precede (c: CHARACTER_32)
			-- Add c at front.
			-- Was declared in STRING_32 as synonym of prepend_character.
		local
			l_area: like area
		do
			if count = capacity then
				resize (count + additional_space)
			end
			l_area := area;
			l_area.overlapping_move (0, 1, count);
			l_area.put (c, 0)
			count := count + 1
			reset_hash_codes
		ensure
			new_count: count = old count + 1
		end

	prepend (s: READABLE_STRING_32)
			-- Prepend characters of s at front.
		require
			argument_not_void: s /= Void
		do
			insert_string (s, 1)
		ensure
			new_count: count = old (count + s.count)
			inserted: Elks_checking implies same_string (old (s + Current))
		end

	prepend_boolean (b: BOOLEAN)
			-- Prepend the string representation of b at front.
		do
			prepend_string_general (b.out)
		end

	prepend_character (c: CHARACTER_32)
			-- Add c at front.
			-- Was declared in STRING_32 as synonym of precede.
		local
			l_area: like area
		do
			if count = capacity then
				resize (count + additional_space)
			end
			l_area := area;
			l_area.overlapping_move (0, 1, count);
			l_area.put (c, 0)
			count := count + 1
			reset_hash_codes
		ensure
			new_count: count = old count + 1
		end

	prepend_double (d: REAL_64)
			-- Prepend the string representation of d at front.
		do
			prepend_string_general (d.out)
		end

	prepend_integer (i: INTEGER_32)
			-- Prepend the string representation of i at front.
		do
			prepend_string_general (i.out)
		end

	prepend_real (r: REAL_32)
			-- Prepend the string representation of r at front.
		do
			prepend_string_general (r.out)
		end

	prepend_string (s: detachable READABLE_STRING_32)
			-- Prepend characters of s, if not void, at front.
		do
			if s /= Void then
				prepend (s)
			end
		end

	prepend_string_general (s: READABLE_STRING_GENERAL)
			-- Prepend characters of s at front.
		require -- from STRING_GENERAL
			argument_not_void: s /= Void
			compatible_strings: Is_string_8 implies s.is_valid_as_string_8
		do
			if attached {READABLE_STRING_32} s as l_s32 then
				prepend (l_s32)
			else
				Precursor {STRING_GENERAL} (s)
			end
		ensure -- from STRING_GENERAL
			new_count: count = old (count + s.count)
			inserted: Elks_checking implies same_string_general (old (s.to_string_32 + Current.as_string_32))
		end

	prepend_substring (s: READABLE_STRING_32; start_index, end_index: INTEGER_32)
			-- Prepend characters of s.substring (start_index, end_index) at front.
		require
			argument_not_void: s /= Void
			start_index_valid: start_index >= 1
			end_index_valid: end_index <= s.count
			valid_bounds: start_index <= end_index + 1
		local
			new_size: INTEGER_32
			l_s_count: INTEGER_32
			l_area: like area
		do
			l_s_count := end_index - start_index + 1
			if l_s_count > 0 then
				new_size := l_s_count + count
				if new_size > capacity then
					resize (new_size + additional_space)
				end
				l_area := area;
				l_area.overlapping_move (0, l_s_count, count);
				l_area.copy_data (s.area, s.area_lower + start_index - 1, 0, l_s_count)
				count := new_size
				reset_hash_codes
			end
		ensure
			new_count: count = old count + end_index - start_index + 1
			inserted: Elks_checking implies same_string (old (s.substring (start_index, end_index) + Current))
		end

	prepend_substring_general (s: READABLE_STRING_GENERAL; start_index, end_index: INTEGER_32)
			-- Prepend characters of s.substring (start_index, end_index) at front.
			-- (from STRING_GENERAL)
		require -- from STRING_GENERAL
			argument_not_void: s /= Void
			compatible_strings: Is_string_8 implies s.is_valid_as_string_8
			start_index_valid: start_index >= 1
			end_index_valid: end_index <= s.count
			valid_bounds: start_index <= end_index + 1
		local
			l_count, l_s_count, l_new_size: INTEGER_32
			i, j: INTEGER_32
		do
			l_s_count := end_index - start_index + 1
			if l_s_count > 0 then
				l_count := count
				l_new_size := l_s_count + l_count
				if l_new_size > capacity then
					resize (l_new_size)
				end
				set_count (l_new_size)
				from
					i := l_count
				until
					i = 0
				loop
					put_code (code (i), i + l_s_count)
					i := i - 1
				end
				from
					i := start_index
					j := 1
				until
					i > end_index
				loop
					put_code (s.code (i), j)
					i := i + 1
					j := j + 1
				end
				reset_hash_codes
			end
		ensure -- from STRING_GENERAL
			new_count: count = old count + end_index - start_index + 1
			inserted: Elks_checking implies same_string_general (old (s.substring (start_index, end_index).to_string_32 + Current.as_string_32))
		end

	put (c: CHARACTER_32; i: INTEGER_32)
			-- Replace character at position i by c.
		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 (c, i - 1)
			reset_hash_codes
		ensure -- from TABLE
			inserted: item (i) = c
		ensure -- from TO_SPECIAL
			inserted: item (i) = c
		ensure then
			stable_count: count = old count
			stable_before_i: Elks_checking implies substring (1, i - 1) ~ (old substring (1, i - 1))
			stable_after_i: Elks_checking implies substring (i + 1, count) ~ (old substring (i + 1, count))
		end

	put_code (v: NATURAL_32; i: INTEGER_32)
			-- Replace character at position i by character of code v.
		require -- from STRING_GENERAL
			valid_code: valid_code (v)
			valid_index: valid_index (i)
		do
			area.put (v.to_character_32, i - 1)
			reset_hash_codes
		ensure -- from STRING_GENERAL
			inserted: code (i) = v
			stable_count: count = old count
			stable_before_i: Elks_checking implies substring (1, i - 1) ~ (old substring (1, i - 1))
			stable_after_i: Elks_checking implies substring (i + 1, count) ~ (old substring (i + 1, count))
		end

	replace_blank
			-- Replace all current characters with blanks.
		do
			fill_with (' '.to_character_32)
		ensure
			same_size: (count = old count) and (capacity = old capacity)
			all_blank: Elks_checking implies occurrences (' '.to_character_32) = count
		end

	replace_character (c: CHARACTER_32)
		obsolete "ELKS 2001: use `fill_with' instead'. [2017-05-31]"
			-- Replace every character with c.
		do
			fill_with (c)
		ensure
			same_count: (count = old count) and (capacity = old capacity)
			filled: Elks_checking implies occurrences (c) = count
		end

	replace_substring (s: READABLE_STRING_32; start_index, end_index: INTEGER_32)
			-- Replace characters from start_index to end_index with s.
		require
			string_not_void: s /= Void
			valid_start_index: 1 <= start_index
			valid_end_index: end_index <= count
			meaningfull_interval: start_index <= end_index + 1
		local
			new_size: INTEGER_32
			diff: INTEGER_32
			l_area: like area
			s_count: INTEGER_32
			old_count: INTEGER_32
		do
			s_count := s.count
			old_count := count
			diff := s_count - (end_index - start_index + 1)
			new_size := diff + old_count
			if diff > 0 then
				grow (new_size)
			end
			l_area := area
			if diff /= 0 then
				l_area.overlapping_move (end_index, end_index + diff, old_count - end_index)
			end
			set_count (new_size);
			l_area.copy_data (s.area, s.area_lower, start_index - 1, s_count)
		ensure
			new_count: count = old count + old s.count - end_index + start_index - 1
			replaced: Elks_checking implies (Current ~ (old (substring (1, start_index - 1) + s + substring (end_index + 1, count))))
		end

	replace_substring_all (original, new: READABLE_STRING_32)
			-- Replace every occurrence of original with new.
		require
			original_exists: original /= Void
			new_exists: new /= Void
			original_not_empty: not original.is_empty
		local
			l_first_pos, l_next_pos: INTEGER_32
			l_orig_count, l_new_count, l_new_lower, l_count, i, l_index_count: INTEGER_32
			l_src_index, l_dest_index, l_prev_index, l_copy_delta: INTEGER_32
			l_area, l_new_area: like area
			l_offset: INTEGER_32
			l_string_searcher: like String_searcher
			l_index_list: SPECIAL [INTEGER_32]
		do
			if not is_empty then
				l_count := count
				l_string_searcher := String_searcher;
				l_string_searcher.initialize_deltas (original)
				l_orig_count := original.count
				l_new_count := new.count
				if l_orig_count >= l_new_count then
					l_first_pos := l_string_searcher.substring_index_with_deltas (Current, original, 1, l_count)
					if l_first_pos > 0 then
						if l_orig_count = l_new_count then
							from
								l_area := area
								l_new_area := new.area
								l_new_lower := new.area_lower
							until
								l_first_pos = 0
							loop
								l_area.copy_data (l_new_area, l_new_lower, l_first_pos - 1, l_new_count)
								if l_first_pos + l_new_count <= l_count then
									l_first_pos := l_string_searcher.substring_index_with_deltas (Current, original, l_first_pos + l_new_count, l_count)
								else
									l_first_pos := 0
								end
							end
						elseif l_orig_count > l_new_count then
							from
								l_next_pos := l_string_searcher.substring_index_with_deltas (Current, original, l_first_pos + l_orig_count, l_count)
								l_area := area
								l_new_area := new.area
								l_new_lower := new.area_lower
							until
								l_next_pos = 0
							loop
								l_area.copy_data (l_new_area, l_new_lower, l_first_pos - 1 - l_offset, l_new_count);
								l_area.overlapping_move (l_first_pos + l_orig_count - 1, l_first_pos + l_new_count - 1 - l_offset, l_next_pos - l_first_pos - l_orig_count)
								l_first_pos := l_next_pos
								l_offset := l_offset + (l_orig_count - l_new_count)
								if l_first_pos + l_new_count <= l_count then
									l_next_pos := l_string_searcher.substring_index_with_deltas (Current, original, l_first_pos + l_orig_count, l_count)
								else
									l_next_pos := 0
								end
							end;
							l_area.copy_data (l_new_area, l_new_lower, l_first_pos - 1 - l_offset, l_new_count);
							l_area.overlapping_move (l_first_pos + l_orig_count - 1, l_first_pos + l_new_count - 1 - l_offset, l_count + 1 - l_first_pos - l_orig_count)
							l_offset := l_offset + (l_orig_count - l_new_count)
							set_count (l_count - l_offset)
						end
						reset_hash_codes
					end
				elseif attached l_string_searcher.substring_index_list_with_deltas (Current, original, 1, l_count) as l_list then
					l_index_list := l_list.area
					l_index_count := l_index_list.count
					l_prev_index := l_count
					l_copy_delta := l_new_count - l_orig_count
					l_count := l_count + (l_index_count * l_copy_delta)
					l_area := area.resized_area_with_default ('%U'.to_character_32, l_count + 1)
					area := l_area
					from
						i := l_index_count
						l_new_lower := new.area_lower
						l_new_area := new.area
					until
						i = 0
					loop
						i := i - 1
						l_src_index := l_index_list.item (i)
						l_dest_index := l_src_index + i * l_copy_delta;
						l_area.overlapping_move (l_src_index + l_orig_count - 1, l_dest_index + l_new_count - 1, l_prev_index - l_src_index - l_orig_count + 1)
						l_prev_index := l_src_index - 1;
						l_area.copy_data (l_new_area, l_new_lower, l_dest_index - 1, l_new_count)
					end
					set_count (l_count)
				end
			end
		end

	right_adjust
			-- Remove trailing whitespace.
		local
			i, nb: INTEGER_32
			nb_space: INTEGER_32
			l_area: like area
			c: CHARACTER_32
			l_prop: like Character_properties
		do
			l_prop := Character_properties
			from
				nb := count - 1
				i := nb
				l_area := area
			until
				i < 0
			loop
				c := l_area.item (i)
				if not l_prop.is_space (c) then
					i := -1
				else
					nb_space := nb_space + 1
					i := i - 1
				end
			end
			if nb_space > 0 then
				count := nb + 1 - nb_space
				reset_hash_codes
			end
		ensure -- from STRING_GENERAL
			valid_count: count <= old count
			new_count: not is_empty implies not item (count).is_space
			kept: Elks_checking implies Current ~ (old twin).substring (1, count)
			only_spaces_removed_after: Elks_checking implies (old twin).is_substring_whitespace ((old twin).substring_index (Current, 1) + count, old count)
		end

	set (t: READABLE_STRING_32; n1, n2: INTEGER_32)
			-- Set current string to substring of t from indices n1
			-- to n2, or to empty string if no such substring.
		require
			argument_not_void: t /= Void
		local
			s: READABLE_STRING_32
		do
			s := t.substring (n1, n2)
			area := s.area
			count := s.count
			reset_hash_codes
		ensure
			is_substring: same_string (t.substring (n1, n2))
		end

	share (other: STRING_32)
			-- Make current string share the text of other.
			-- Subsequent changes to the characters of current string
			-- will also affect other, and conversely.
		require
			argument_not_void: other /= Void
		do
			area := other.area
			count := other.count
			reset_hash_codes
		ensure
			shared_count: other.count = count
			shared_area: other.area = area
		end

	subcopy (other: READABLE_STRING_32; start_pos, end_pos, index_pos: INTEGER_32)
			-- Copy characters of other within bounds start_pos and
			-- end_pos to current string starting at index index_pos.
		require
			other_not_void: other /= Void
			valid_start_pos: other.valid_index (start_pos)
			valid_end_pos: other.valid_index (end_pos)
			valid_bounds: start_pos <= end_pos or start_pos = end_pos + 1
			valid_index_pos: valid_index (index_pos)
			enough_space: count - index_pos >= end_pos - start_pos
		local
			l_other_area, l_area: like area
		do
			if end_pos >= start_pos then
				l_other_area := other.area
				l_area := area
				if l_area = l_other_area then
					l_area.overlapping_move (start_pos - 1, index_pos - 1, end_pos - start_pos + 1)
				else
					l_area.copy_data (l_other_area, start_pos - 1, index_pos - 1, end_pos - start_pos + 1)
				end
				reset_hash_codes
			end
		ensure
			same_count: count = old count
			copied: Elks_checking implies (Current ~ (old substring (1, index_pos - 1) + old other.substring (start_pos, end_pos) + old substring (index_pos + (end_pos - start_pos + 1), count)))
		end
	
feature {NONE} -- 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
		obsolete "Use `wipe_out' instead. [2017-05-31]"
			-- Reset all characters.
		do
			count := 0
			reset_hash_codes
		ensure
			is_empty: count = 0
			same_capacity: capacity = old capacity
		end

	prune (c: CHARACTER_32)
			-- Remove first occurrence of c, if any.
		require -- from COLLECTION
			prunable: prunable
		require else
				True
		local
			counter: INTEGER_32
		do
			from
				counter := 1
			until
				counter > count or else (item (counter) = c)
			loop
				counter := counter + 1
			end
			if counter <= count then
				remove (counter)
			end
		end

	prune_all (c: CHARACTER_32)
			-- Remove all occurrences of c.
		require -- from COLLECTION
			prunable: prunable
		require else
				True
		local
			i, j, nb: INTEGER_32
			l_area: like area
			l_char: CHARACTER_32
		do
			from
				l_area := area
				nb := count
			until
				i = nb
			loop
				l_char := l_area.item (i)
				if l_char /= c then
					l_area.put (l_char, j)
					j := j + 1
				end
				i := i + 1
			end
			count := j
			reset_hash_codes
		ensure -- from COLLECTION
			no_more_occurrences: not has (c)
		ensure then
			changed_count: count = (old count) - (old occurrences (c))
		end

	prune_all_leading (c: CHARACTER_32)
			-- Remove all leading occurrences of c.
		do
			from
			until
				is_empty or else item (1) /= c
			loop
				remove (1)
			end
		end

	prune_all_trailing (c: CHARACTER_32)
			-- Remove all trailing occurrences of c.
		do
			from
			until
				is_empty or else item (count) /= c
			loop
				remove (count)
			end
		end

	remove (i: INTEGER_32)
			-- Remove i-th character.
		require -- from STRING_GENERAL
			valid_index: valid_index (i)
		require -- from DYNAMIC_TABLE
			prunable: prunable
			valid_key: valid_index (i)
		local
			l_count: INTEGER_32
		do
			l_count := count;
			area.overlapping_move (i, i - 1, l_count - i)
			count := l_count - 1
			reset_hash_codes
		ensure -- from STRING_GENERAL
			new_count: count = old count - 1
			removed: Elks_checking implies to_string_32 ~ (old substring (1, i - 1).to_string_32 + old substring (i + 1, count).to_string_32)
		end

	remove_head (n: INTEGER_32)
			-- Remove first n characters;
			-- if n > count, remove all.
		require -- from STRING_GENERAL
			n_non_negative: n >= 0
		do
			if n > count then
				count := 0
				reset_hash_codes
			else
				keep_tail (count - n)
			end
		ensure -- from STRING_GENERAL
			removed: Elks_checking implies Current ~ (old substring (n.min (count) + 1, count))
		end

	remove_substring (start_index, end_index: INTEGER_32)
			-- Remove all characters from start_index
			-- to end_index inclusive.
		require -- from STRING_GENERAL
			valid_start_index: 1 <= start_index
			valid_end_index: end_index <= count
			meaningful_interval: start_index <= end_index + 1
		local
			l_count, nb_removed: INTEGER_32
		do
			nb_removed := end_index - start_index + 1
			if nb_removed > 0 then
				l_count := count;
				area.overlapping_move (start_index + nb_removed - 1, start_index - 1, l_count - end_index)
				count := l_count - nb_removed
				reset_hash_codes
			end
		ensure -- from STRING_GENERAL
			removed: Elks_checking implies Current.as_string_32 ~ (old substring (1, start_index - 1).as_string_32 + old substring (end_index + 1, count).as_string_32)
		end

	remove_tail (n: INTEGER_32)
			-- Remove last n characters;
			-- if n > count, remove all.
		require -- from STRING_GENERAL
			n_non_negative: n >= 0
		local
			l_count: INTEGER_32
		do
			l_count := count
			if n > l_count then
				count := 0
				reset_hash_codes
			else
				keep_head (l_count - n)
			end
		ensure -- from STRING_GENERAL
			removed: Elks_checking implies Current ~ (old substring (1, count - n.min (count)))
		end

	wipe_out
			-- Remove all characters.
		require -- from  STRING_GENERAL
			True
		require -- from COLLECTION
			prunable: prunable
		do
			count := 0
			reset_hash_codes
		ensure -- from STRING_GENERAL
			is_empty: count = 0
			same_capacity: capacity = old capacity
		ensure -- from COLLECTION
			wiped_out: is_empty
		end
	
feature -- Resizing

	adapt_size
			-- Adapt the size to accommodate count characters.
		do
			resize (count)
		end

	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 (newsize: INTEGER_32)
			-- Ensure that the capacity is at least newsize.
		require -- from RESIZABLE
			resizable: resizable
		do
			if newsize > capacity then
				resize (newsize)
			end
		ensure -- from RESIZABLE
			new_capacity: capacity >= newsize
		end

	resize (newsize: INTEGER_32)
			-- Rearrange string so that it can accommodate
			-- at least newsize characters.
			-- Do not lose any previously entered character.
		require -- from STRING_GENERAL
			new_size_large_enough: newsize >= count
		do
			area := area.aliased_resized_area_with_default ('%U'.to_character_32, newsize + 1)
		ensure -- from STRING_GENERAL
			same_count: count = old count
			capacity_large_enough: capacity >= newsize
			same_content: Elks_checking implies same_string_general (old twin)
		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 + 1)
			end
		ensure -- from RESIZABLE
			same_count: count = old count
			minimal_capacity: capacity = count
		ensure then
			same_string: same_string (old twin)
		end
	
feature -- Transformation

	correct_mismatch
			-- Attempt to correct object mismatch during retrieve using Mismatch_information.
		do
			if area = Void and then attached {like area} Mismatch_information.item ("area") as l_area then
				area := l_area
			end
		end
	
feature -- Conversion

	as_lower: like Current
			-- New object with all letters in lower case.
		do
			Result := twin;
			Result.to_lower
		ensure -- from READABLE_STRING_GENERAL
			as_lower_attached: Result /= Void
			length: Result.count = count
			anchor: count > 0 implies Result.item (1) = item (1).as_lower
			recurse: count > 1 implies Result.substring (2, count) ~ substring (2, count).as_lower
		end

	as_readable_string_32: READABLE_STRING_32
		obsolete "Use explicit conversion `to_string_32`, or, better use READABLE_STRING_32 and descendants instead. [2017-05-31]"
			-- Equivalent to as_string_32 with a different name.
			-- (from READABLE_STRING_GENERAL)
		do
			Result := as_string_32
		end

	as_readable_string_8: READABLE_STRING_8
		obsolete "Use explicit conversion `to_string_8' with a test that the string is made of ASCII characters only. [2017-05-31]"
			-- Convert Current as a READABLE_STRING_8. If a code of Current is
			-- not a valid code for a READABLE_STRING_8 it is replaced with the null
			-- character.
			-- (from READABLE_STRING_GENERAL)
		do
			Result := as_string_8
		end

	as_string_32: STRING_32
			-- Convert Current as a STRING_32.
			-- Was declared in READABLE_STRING_GENERAL as synonym of to_string_32.
			-- (from READABLE_STRING_GENERAL)
		local
			i, nb: INTEGER_32
		do
			if attached {STRING_32} Current as l_result then
				Result := l_result
			else
				nb := count
				create Result.make (nb);
				Result.set_count (nb)
				from
					i := 1
				until
					i > nb
				loop
					Result.put_code (code (i), i)
					i := i + 1
				end
			end
		ensure -- from READABLE_STRING_GENERAL
			as_string_32_not_void: Result /= Void
			identity: (conforms_to (create {STRING_32}.make_empty) and Result = Current) or (not conforms_to (create {STRING_32}.make_empty) and Result /= Current)
		end

	as_string_32_conversion: STRING_32
		obsolete "Update target of call to use READABLE_STRING_32 and descendants instead. [2017-05-31]"
			-- Equivalent to as_string_32 with a different name.
			-- To be used for migrating existing code to Unicode
			-- when you get a compiler error but cannot or do not have
			-- the time yet to address the source of the string to be
			-- a READABLE_STRING_32 or descendants.
			-- (from READABLE_STRING_GENERAL)
		do
			Result := as_string_32
		end

	as_string_8: STRING_8
		obsolete "[
			For 32-bit strings:
				- use explicit conversion `to_string_8` with a test that the string is made of ASCII characters only.
			For 8-bit strings:
				- consider changing the type of reattachmanet target to READABLE_STRING_8 or
				- use explicit conversion `to_string_8` to avoid implicit performance penalty.
			[2019-11-30]
		]"
			-- Convert Current as a STRING_8. If a code of Current is
			-- not a valid code for a STRING_8 it is replaced with the null
			-- character.
			-- (from READABLE_STRING_GENERAL)
		local
			i, nb: INTEGER_32
			l_code: like code
		do
			if attached {STRING_8} Current as l_result then
				Result := l_result
			else
				nb := count
				create Result.make (nb);
				Result.set_count (nb)
				from
					i := 1
				until
					i > nb
				loop
					l_code := code (i)
					if Result.valid_code (l_code) then
						Result.put_code (l_code, i)
					else
						Result.put_code (0, i)
					end
					i := i + 1
				end
			end
		ensure -- from READABLE_STRING_GENERAL
			as_string_8_not_void: Result /= Void
			identity: (conforms_to ("") and Result = Current) or (not conforms_to ("") and Result /= Current)
		end

	as_string_8_conversion: STRING_8
		obsolete "Update recipient of call to use READABLE_STRING_32 and descendants instead. [2017-05-31]"
			-- Equivalent to as_string_8 with a different name.
			-- To be used for migrating existing code to Unicode
			-- when you get a compiler error but cannot or do not have
			-- the time yet to address the target recipient of the string to be
			-- a READABLE_STRING_32 or descendants.
			-- (from READABLE_STRING_GENERAL)
		do
			Result := as_string_8
		end

	as_upper: like Current
			-- New object with all letters in upper case
		do
			Result := twin;
			Result.to_upper
		ensure -- from READABLE_STRING_GENERAL
			as_upper_attached: Result /= Void
			length: Result.count = count
			anchor: count > 0 implies Result.item (1) = item (1).as_upper
			recurse: count > 1 implies Result.substring (2, count) ~ substring (2, count).as_upper
		end

	center_justify
			-- Center justify Current using count as width.
		local
			i, nb, l_offset: INTEGER_32
			left_nb_space, right_nb_space: INTEGER_32
			l_area: like area
			l_prop: like Character_properties
		do
			l_prop := Character_properties
			from
				nb := count
				l_area := area
			until
				left_nb_space = nb or else not l_prop.is_space (l_area.item (left_nb_space))
			loop
				left_nb_space := left_nb_space + 1
			end
			from
				i := nb - 1
				l_area := area
			until
				i = -1 or else not l_prop.is_space (l_area.item (i))
			loop
				right_nb_space := right_nb_space + 1
				i := i - 1
			end
			l_offset := left_nb_space + right_nb_space
			if l_offset \\ 2 = 0 then
				l_offset := left_nb_space - l_offset // 2
			else
				l_offset := left_nb_space - l_offset // 2 - 1
			end
			if l_offset /= 0 then
				l_area.move_data (left_nb_space, left_nb_space - l_offset, nb - left_nb_space - right_nb_space)
				if l_offset < 0 then
					l_area.fill_with (' '.to_character_32, left_nb_space, left_nb_space - l_offset - 1)
				else
					l_area.fill_with (' '.to_character_32, nb - right_nb_space - l_offset, nb - 1)
				end
				reset_hash_codes
			end
		end

	character_justify (pivot: CHARACTER_32; position: INTEGER_32)
			-- Justify a string based on a pivot
			-- and the position it needs to be in
			-- the final string.
			-- This will grow the string if necessary
			-- to get the pivot in the correct place.
		require
			valid_position: position <= capacity
			positive_position: position >= 1
			pivot_not_space: pivot /= ' '.to_character_32
			not_empty: not is_empty
		local
			l_index_of_pivot, l_new_size: INTEGER_32
			l_area: like area
		do
			l_index_of_pivot := index_of (pivot, 1)
			if l_index_of_pivot /= 0 then
				if l_index_of_pivot < position then
					l_new_size := count + position - l_index_of_pivot
					grow (l_new_size)
					l_area := area;
					l_area.move_data (0, position - l_index_of_pivot, count);
					l_area.fill_with (' '.to_character_32, 0, position - l_index_of_pivot - 1)
					count := l_new_size
				else
					l_area := area;
					l_area.move_data (l_index_of_pivot - position, 0, count - l_index_of_pivot + position);
					l_area.fill_with (' '.to_character_32, count - l_index_of_pivot + position, count - 1)
				end
				reset_hash_codes
			end
		end

	left_justify
			-- Left justify Current using count as witdth.
		local
			i, nb: INTEGER_32
			l_area: like area
		do
			nb := count
			left_adjust
			i := count
			if i < nb then
				from
					l_area := area
				until
					i = nb
				loop
					l_area.put (' '.to_character_32, i)
					i := i + 1
				end
				count := nb
				reset_hash_codes
			end
		end

	linear_representation: LINEAR [CHARACTER_32]
			-- Representation as a linear structure
		local
			temp: ARRAYED_LIST [CHARACTER_32]
			i: INTEGER_32
		do
			create temp.make (capacity)
			from
				i := 1
			until
				i > count
			loop
				temp.extend (item (i))
				i := i + 1
			end
			Result := temp
		end

	mirror
			-- Reverse the order of characters.
			-- "Hello world" -> "dlrow olleH".
		local
			a: like area
			c: CHARACTER_32
			i, j: INTEGER_32
		do
			if count > 0 then
				from
					i := count - 1
					a := area
				until
					i <= j
				loop
					c := a.item (i);
					a.put (a.item (j), i);
					a.put (c, j)
					i := i - 1
					j := j + 1
				end
				reset_hash_codes
			end
		ensure
			same_count: count = old count
		end

	mirrored: like Current
			-- Mirror image of string;
			-- Result for "Hello world" is "dlrow olleH".
		do
			Result := twin
			if count > 0 then
				Result.mirror
			end
		ensure -- from READABLE_STRING_32
			same_count: Result.count = count
		end

	right_justify
			-- Right justify Current using count as width.
		local
			i, nb: INTEGER_32
			nb_space: INTEGER_32
			l_area: like area
		do
			nb := count
			right_adjust
			i := count
			nb_space := nb - i
			if nb_space > 0 then
				from
					l_area := area
				variant
						i + 1
				until
					i = 0
				loop
					i := i - 1;
					l_area.put (l_area.item (i), i + nb_space)
				end
				from
				variant
						nb_space + 1
				until
					nb_space = 0
				loop
					nb_space := nb_space - 1;
					l_area.put (' '.to_character_32, nb_space)
				end
				count := nb
				reset_hash_codes
			end
		ensure
			same_count: count = old count
		end

	split (a_separator: CHARACTER_32): LIST [STRING_32]
			-- Split on a_separator.
			-- (from READABLE_STRING_GENERAL)
		local
			l_list: ARRAYED_LIST [STRING_32]
			i, j, c: INTEGER_32
		do
			c := count
			create l_list.make (c + 1)
			if c > 0 then
				from
					i := 1
				until
					i > c
				loop
					j := index_of (a_separator, i)
					if j = 0 then
						j := c + 1
					end;
					l_list.extend (substring (i, j - 1))
					i := j + 1
				end
				if j = c then
					check
						last_character_is_a_separator: item (j) = a_separator
					end;
					l_list.extend (new_string (0))
				end
			else
				l_list.extend (new_string (0))
			end
			Result := l_list
			check
					l_list.count = occurrences (a_separator) + 1
			end
		ensure -- from READABLE_STRING_GENERAL
				Result /= Void
		end

	to_boolean: BOOLEAN
			-- Boolean value;
			-- "True" yields True, "False" yields False
			-- (case-insensitive)
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_boolean: is_boolean
		do
			check
					True_constant.count = 4
			end
			if count = 4 then
				Result := True
			end
		ensure -- from READABLE_STRING_GENERAL
			to_boolean: (Result = as_lower.same_string_general (True_constant)) or (not Result = as_lower.same_string_general (False_constant))
		end

	frozen to_c: ANY
			-- A reference to a C form of current string.
			-- Useful only for interfacing with C software.
		require
			not_is_dotnet: not {PLATFORM}.is_dotnet
		local
			l_area: like area
		do
			l_area := area;
			l_area.put ('%U'.to_character_32, count)
			Result := l_area
		end

	frozen to_cil: SYSTEM_STRING
			-- Create an instance of SYSTEM_STRING using characters
			-- of Current between indices 1 and count.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_dotnet: {PLATFORM}.is_dotnet
		do
			Result := Dotnet_convertor.from_string_to_system_string (Current)
		ensure -- from READABLE_STRING_GENERAL
			to_cil_not_void: Result /= Void
		end

	to_double: REAL_64
			-- "Double" value;
			-- for example, when applied to "123.0", will yield 123.0 (double)
			-- Was declared in READABLE_STRING_GENERAL as synonym of to_real_64.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			represents_a_double: is_double
		local
			l_convertor: like Ctor_convertor
		do
			l_convertor := Ctor_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_no_limitation)
			Result := l_convertor.parsed_double
		end

	to_integer: INTEGER_32
			-- 32-bit integer value
			-- Was declared in READABLE_STRING_GENERAL as synonym of to_integer_32.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_integer: is_integer_32
		local
			l_convertor: like Ctoi_convertor
		do
			l_convertor := Ctoi_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_no_limitation)
			Result := l_convertor.parsed_integer
		end

	to_integer_16: INTEGER_16
			-- 16-bit integer value
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_integer_16: is_integer_16
		local
			l_convertor: like Ctoi_convertor
		do
			l_convertor := Ctoi_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_no_limitation)
			Result := l_convertor.parsed_integer_16
		end

	to_integer_32: INTEGER_32
			-- 32-bit integer value
			-- Was declared in READABLE_STRING_GENERAL as synonym of to_integer.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_integer: is_integer_32
		local
			l_convertor: like Ctoi_convertor
		do
			l_convertor := Ctoi_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_no_limitation)
			Result := l_convertor.parsed_integer
		end

	to_integer_64: INTEGER_64
			-- 64-bit integer value
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_integer_64: is_integer_64
		local
			l_convertor: like Ctoi_convertor
		do
			l_convertor := Ctoi_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_no_limitation)
			Result := l_convertor.parsed_integer_64
		end

	to_integer_8: INTEGER_8
			-- 8-bit integer value
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_integer_8: is_integer_8
		local
			l_convertor: like Ctoi_convertor
		do
			l_convertor := Ctoi_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_no_limitation)
			Result := l_convertor.parsed_integer_8
		end

	to_lower
			-- Convert to lower case.
		do
			to_lower_area (area, 0, count - 1)
			reset_hash_codes
		ensure
			length_and_content: Elks_checking implies Current ~ (old as_lower)
		end

	to_natural: NATURAL_32
			-- 32-bit natural value
			-- Was declared in READABLE_STRING_GENERAL as synonym of to_natural_32.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_natural: is_natural_32
		local
			l_convertor: like Ctoi_convertor
		do
			l_convertor := Ctoi_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_no_limitation)
			Result := l_convertor.parsed_natural_32
		end

	to_natural_16: NATURAL_16
			-- 16-bit natural value
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_natural_16: is_natural_16
		local
			l_convertor: like Ctoi_convertor
		do
			l_convertor := Ctoi_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_no_limitation)
			Result := l_convertor.parsed_natural_16
		end

	to_natural_32: NATURAL_32
			-- 32-bit natural value
			-- Was declared in READABLE_STRING_GENERAL as synonym of to_natural.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_natural: is_natural_32
		local
			l_convertor: like Ctoi_convertor
		do
			l_convertor := Ctoi_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_no_limitation)
			Result := l_convertor.parsed_natural_32
		end

	to_natural_64: NATURAL_64
			-- 64-bit natural value
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_natural_64: is_natural_64
		local
			l_convertor: like Ctoi_convertor
		do
			l_convertor := Ctoi_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_no_limitation)
			Result := l_convertor.parsed_natural_64
		end

	to_natural_8: NATURAL_8
			-- 8-bit natural value
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_natural_8: is_natural_8
		local
			l_convertor: like Ctoi_convertor
		do
			l_convertor := Ctoi_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_no_limitation)
			Result := l_convertor.parsed_natural_8
		end

	to_real: REAL_32
			-- Real value;
			-- for example, when applied to "123.0", will yield 123.0
			-- Was declared in READABLE_STRING_GENERAL as synonym of to_real_32.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			represents_a_real: is_real
		do
			Result := to_double.truncated_to_real
		end

	to_real_32: REAL_32
			-- Real value;
			-- for example, when applied to "123.0", will yield 123.0
			-- Was declared in READABLE_STRING_GENERAL as synonym of to_real.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			represents_a_real: is_real
		do
			Result := to_double.truncated_to_real
		end

	to_real_64: REAL_64
			-- "Double" value;
			-- for example, when applied to "123.0", will yield 123.0 (double)
			-- Was declared in READABLE_STRING_GENERAL as synonym of to_double.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			represents_a_double: is_double
		local
			l_convertor: like Ctor_convertor
		do
			l_convertor := Ctor_convertor;
			l_convertor.parse_string_with_type (Current, {NUMERIC_INFORMATION}.type_no_limitation)
			Result := l_convertor.parsed_double
		end

	to_string_32: STRING_32
			-- Convert Current as a STRING_32.
			-- Was declared in READABLE_STRING_GENERAL as synonym of as_string_32.
			-- (from READABLE_STRING_GENERAL)
		local
			i, nb: INTEGER_32
		do
			if attached {STRING_32} Current as l_result then
				Result := l_result
			else
				nb := count
				create Result.make (nb);
				Result.set_count (nb)
				from
					i := 1
				until
					i > nb
				loop
					Result.put_code (code (i), i)
					i := i + 1
				end
			end
		ensure -- from READABLE_STRING_GENERAL
			as_string_32_not_void: Result /= Void
			identity: (conforms_to (create {STRING_32}.make_empty) and Result = Current) or (not conforms_to (create {STRING_32}.make_empty) and Result /= Current)
		end

	to_string_8: STRING_8
			-- Convert Current as a STRING_8.
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_valid_as_string_8: is_valid_as_string_8
		local
			i, nb: INTEGER_32
		do
			if attached {STRING_8} Current as s then
				Result := s
			else
				nb := count
				create Result.make (nb);
				Result.set_count (nb)
				from
					i := 1
				until
					i > nb
				loop
					check
						from_precondition: Result.valid_code (code (i))
					end;
					Result.put_code (code (i), i)
					i := i + 1
				end
			end
		ensure -- from READABLE_STRING_GENERAL
			as_string_8_not_void: Result /= Void
			identity: (conforms_to ("") and Result = Current) or (not conforms_to ("") and Result /= Current)
		end

	to_upper
			-- Convert to upper case.
		do
			to_upper_area (area, 0, count - 1)
			reset_hash_codes
		ensure
			length_and_content: Elks_checking implies Current ~ (old as_upper)
		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: STRING_32)
			-- Reinitialize by copying the characters of other.
			-- (This is also used by twin.)
			-- (from READABLE_STRING_32)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		local
			old_area: like area
		do
			if other /= Current then
				old_area := area
				standard_copy (other)
				if old_area = Void or else old_area = other.area or else old_area.count <= count then
					area := area.resized_area (count + 1)
				else
					old_area.copy_data (area, 0, 0, count)
					area := old_area
				end
				internal_hash_code := 0
			end
		ensure -- from ANY
			is_equal: Current ~ other
		ensure then -- from READABLE_STRING_32
			new_result_count: count = other.count
		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: STRING_32)
			-- 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: STRING_32
			-- 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

	head (n: INTEGER_32): STRING_32
			-- Prefix, retaining first n characters (or as many as available).
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			non_negative_argument: n >= 0
		do
			if n > count then
				Result := twin
			else
				Result := substring (1, n)
			end
		ensure -- from READABLE_STRING_GENERAL
			same_count: count = old count
			new_count: Result.count = n.min (count)
		end

	multiply (n: INTEGER_32)
			-- Duplicate a string within itself
			-- ("hello").multiply(3) => "hellohellohello"
		require
			meaningful_multiplier: n >= 1
		local
			s: like Current
			i: INTEGER_32
		do
			s := twin
			grow (n * count)
			from
				i := n
			until
				i = 1
			loop
				append (s)
				i := i - 1
			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: STRING_32)
			-- 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: STRING_32
			-- 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

	substring (start_index, end_index: INTEGER_32): like Current
			-- Copy of substring containing all characters at indices
			-- between start_index and end_index
		require -- from  READABLE_STRING_GENERAL
			True
		do
			if (1 <= start_index) and (start_index <= end_index) and (end_index <= count) then
				Result := new_string (end_index - start_index + 1);
				Result.area.copy_data (area, start_index - 1, 0, end_index - start_index + 1);
				Result.set_count (end_index - start_index + 1)
			else
				Result := new_string (0)
			end
		ensure -- from READABLE_STRING_GENERAL
			substring_not_void: Result /= Void
			substring_count: Result.count = end_index - start_index + 1 or Result.count = 0
			first_code: Result.count > 0 implies Result.item (1) = item (start_index)
			recurse: Result.count > 0 implies Result.substring (2, Result.count) ~ substring (start_index + 1, end_index)
		end

	tail (n: INTEGER_32): STRING_32
			-- Suffix, retaining last n characters (or as many as available).
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			non_negative_argument: n >= 0
		do
			if n > count then
				Result := twin
			else
				Result := substring (count - n + 1, count)
			end
		ensure -- from READABLE_STRING_GENERAL
			same_count: count = old count
			new_count: Result.count = n.min (count)
		end

	frozen twin: STRING_32
			-- 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 STRING_32
		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 STRING_32
			-- 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

	plus alias "+" (s: READABLE_STRING_32): like Current
			-- Concatenation with s.
		require -- from READABLE_STRING_32
			argument_attached: attached s
		do
			Result := new_string (count + s.count);
			Result.append (Current);
			Result.append (s)
		ensure -- from READABLE_STRING_32
			plus_attached: attached Result
			new_count: Result.count = count + s.count
			initial: Elks_checking implies Result.substring (1, count) ~ Current
			final: Elks_checking implies Result.substring (count + 1, count + s.count).same_string (s)
		end

	plus_general (s: READABLE_STRING_GENERAL): like Current
			-- Concatenation of the current string with s.
		require -- from READABLE_STRING_GENERAL
			argument_not_void: s /= Void
			compatible_strings: Is_string_8 implies s.is_valid_as_string_8
		do
			Result := new_string (count + s.count);
			Result.append (Current);
			Result.append_string_general (s)
		ensure -- from READABLE_STRING_GENERAL
			plus_not_void: Result /= Void
			new_count: Result.count = count + s.count
			initial: Elks_checking implies Result.substring (1, count) ~ Current
			final: Elks_checking implies Result.substring (count + 1, count + s.count).same_string_general (s)
		end
	
feature -- Inapplicable

	bag_put (v: CHARACTER_32)
			-- Ensure that structure includes v.
			-- (from TABLE)
		require -- from COLLECTION
			extendible: Extendible
		do
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		end
	
feature {STRING_HANDLER}{STRING_HANDLER} -- Implementation

	frozen set_count (number: INTEGER_32)
			-- Set count to number of characters.
		require -- from STRING_GENERAL
			valid_count: 0 <= number and number <= capacity
		do
			count := number
			reset_hash_codes
		ensure -- from STRING_GENERAL
			new_count: count = number
		end
	
feature {NONE} -- Implementation

	C_string_provider: C_STRING
			-- To create Eiffel strings from C string.
			-- (from READABLE_STRING_GENERAL)
		once
			create Result.make_empty (0)
		ensure -- from READABLE_STRING_GENERAL
			c_string_provider_not_void: Result /= Void
		end

	Character_properties: CHARACTER_PROPERTY
			-- Access to Unicode character properties
			-- (from READABLE_STRING_GENERAL)
		once
			create Result.make
		end

	Ctoi_convertor: STRING_TO_INTEGER_CONVERTOR
			-- Convertor used to convert string to integer or natural
			-- (from READABLE_STRING_GENERAL)
		once
			create Result.make;
			Result.set_leading_separators (" ");
			Result.set_trailing_separators (" ");
			Result.set_leading_separators_acceptable (True);
			Result.set_trailing_separators_acceptable (True)
		ensure -- from READABLE_STRING_GENERAL
			ctoi_convertor_not_void: Result /= Void
		end

	Ctor_convertor: STRING_TO_REAL_CONVERTOR
			-- Convertor used to convert string to real or double
			-- (from READABLE_STRING_GENERAL)
		once
			create Result.make;
			Result.set_leading_separators (" ");
			Result.set_trailing_separators (" ");
			Result.set_leading_separators_acceptable (True);
			Result.set_trailing_separators_acceptable (True)
		ensure -- from READABLE_STRING_GENERAL
			ctor_convertor_not_void: Result /= Void
		end

	Dotnet_convertor: SYSTEM_STRING_FACTORY
			-- Convertor used to convert from and to SYSTEM_STRING.
			-- (from READABLE_STRING_GENERAL)
		once
			create Result
		ensure -- from READABLE_STRING_GENERAL
			dotnet_convertor_not_void: Result /= Void
		end

	is_valid_integer_or_natural (type: INTEGER_32): BOOLEAN
			-- Is Current a valid number according to given type?
			-- (from READABLE_STRING_GENERAL)
		local
			l_convertor: like Ctoi_convertor
		do
			l_convertor := Ctoi_convertor;
			l_convertor.reset (type);
			l_convertor.parse_string_with_type (Current, type)
			Result := l_convertor.is_integral_integer
		end

	mirror_area (a: like area; start_index, end_index: INTEGER_32)
			-- Mirror all characters in a between start_index and end_index.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			a_not_void: a /= Void
			start_index_non_negative: start_index >= 0
			start_index_not_too_big: start_index <= end_index + 1
			end_index_valid: end_index < a.count
		local
			c: CHARACTER_32
			i, j: INTEGER_32
		do
			from
				i := end_index
			until
				i <= j
			loop
				c := a.item (i);
				a.put (a.item (j), i);
				a.put (c, j)
				i := i - 1
				j := j + 1
			end
		end

	new_string (n: INTEGER_32): like Current
			-- New instance of current with space for at least n characters.
		require -- from READABLE_STRING_GENERAL
			n_non_negative: n >= 0
		do
			create Result.make (n)
		ensure -- from READABLE_STRING_GENERAL
			new_string_not_void: Result /= Void
			new_string_empty: Result.is_empty
			new_string_area_big_enough: Result.capacity >= n
		end

	str_strict_cmp (this, other: like area; this_index, other_index, n: INTEGER_32): INTEGER_32
			-- Compare n characters from this starting at this_index with
			-- n characters from and other starting at other_index.
			-- 0 if equal, < 0 if this < other,
			-- > 0 if this > other
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			this_not_void: this /= Void
			other_not_void: other /= Void
			n_non_negative: n >= 0
			n_valid: n <= (this.upper - this_index + 1) and n <= (other.upper - other_index + 1)
		local
			i, j, nb, l_current_code, l_other_code: INTEGER_32
		do
			from
				i := this_index
				nb := i + n
				j := other_index
			until
				i = nb
			loop
				l_current_code := this.item (i).code
				l_other_code := other.item (j).code
				if l_current_code /= l_other_code then
					Result := l_current_code - l_other_code
					i := nb - 1
				end
				i := i + 1
				j := j + 1
			end
		end

	String_searcher: STRING_32_SEARCHER
			-- String searcher specialized for READABLE_STRING_32 instances.
			-- (from READABLE_STRING_32)
		require -- from  READABLE_STRING_GENERAL
			True
		once
			create Result.make
		ensure -- from READABLE_STRING_GENERAL
			string_searcher_not_void: Result /= Void
		end

	to_lower_area (a: like area; start_index, end_index: INTEGER_32)
			-- Replace all characters in a between start_index and end_index
			-- with their lower version when available.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			a_not_void: a /= Void
			start_index_non_negative: start_index >= 0
			start_index_not_too_big: start_index <= end_index + 1
			end_index_valid: end_index < a.count
		local
			i: INTEGER_32
			c1, c2: CHARACTER_32
			l_prop: like Character_properties
		do
			from
				i := start_index
				l_prop := Character_properties
			until
				i > end_index
			loop
				c1 := a.item (i)
				c2 := l_prop.to_lower (c1)
				if c1 /= c2 then
					a.put (c2, i)
				end
				i := i + 1
			end
		end

	to_upper_area (a: like area; start_index, end_index: INTEGER_32)
			-- Replace all characters in a between start_index and end_index
			-- with their upper version when available.
			-- (from READABLE_STRING_32)
		require -- from READABLE_STRING_32
			a_not_void: a /= Void
			start_index_non_negative: start_index >= 0
			start_index_not_too_big: start_index <= end_index + 1
			end_index_valid: end_index < a.count
		local
			i: INTEGER_32
			c1, c2: CHARACTER_32
			l_prop: like Character_properties
		do
			from
				i := start_index
				l_prop := Character_properties
			until
				i > end_index
			loop
				c1 := a.item (i)
				c2 := l_prop.to_upper (c1)
				if c1 /= c2 then
					a.put (c2, i)
				end
				i := i + 1
			end
		end
	
feature {READABLE_STRING_8, READABLE_STRING_32, STRING_8_SEARCHER, STRING_32_SEARCHER, HEXADECIMAL_STRING_TO_INTEGER_CONVERTER, STRING_TO_INTEGER_CONVERTOR, STRING_TO_REAL_CONVERTOR, STRING_32_ITERATION_CURSOR} -- Implementation

	area_lower: INTEGER_32
			-- Minimum index.
			-- (from READABLE_STRING_32)
		do
		ensure -- from READABLE_STRING_32
			area_lower_non_negative: Result >= 0
			area_lower_valid: Result <= area.upper
		end

	area_upper: INTEGER_32
			-- Maximum index.
			-- (from READABLE_STRING_32)
		do
			Result := area_lower + count - 1
		ensure -- from READABLE_STRING_32
			area_upper_valid: Result <= area.upper
			area_upper_in_bound: area_lower <= Result + 1
		end
	
feature {READABLE_STRING_GENERAL} -- Implementation

	internal_case_insensitive_hash_code: INTEGER_32
			-- Cash for case_insensitive_hash_code.
			-- (from READABLE_STRING_GENERAL)

	internal_hash_code: INTEGER_32
			-- Cache for hash_code.
			-- (from READABLE_STRING_GENERAL)
	
feature -- Access: Cursor

	new_character_32_cursor: STRING_ITERATION_CURSOR
			-- Fresh cursor for this string that iterates over code points (see code)
			-- exposed as CHARACTER_32.
			-- (from READABLE_STRING_GENERAL)
		do
			create Result.make (Current);
			Result.start
		end
	
feature {NONE} -- Assertion helper

	Elks_checking: BOOLEAN = False
			-- Are ELKS checkings verified? Must be True when changing implementation of STRING_GENERAL or descendant.
			-- (from READABLE_STRING_GENERAL)
	
feature -- Correction

	Mismatch_information: MISMATCH_INFORMATION
			-- Original attribute values of mismatched object
			-- (from MISMATCH_CORRECTOR)
		once
			create Result
		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
			-- Printable representation.
			-- (from READABLE_STRING_32)
		require -- from  ANY
			True
		do
			Result := {UTF_CONVERTER}.string_32_to_utf_8_string_8 (Current)
		ensure -- from ANY
			out_not_void: Result /= Void
		ensure then -- from READABLE_STRING_32
			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
	
feature {STRING_HANDLER} -- Settings

	reset_hash_codes
			-- Reset all hash codes of Current string.
			-- (from STRING_GENERAL)
		do
			internal_hash_code := 0
			internal_case_insensitive_hash_code := 0
		end

	set_internal_hash_code (v: like internal_hash_code)
		obsolete "Use `reset_hash_codes` instead. [2017-05-31]"
			-- Set internal_hash_code with v.
			-- (from STRING_GENERAL)
		require -- from STRING_GENERAL
			v_nonnegative: v >= 0
		do
			internal_hash_code := v
		ensure -- from STRING_GENERAL
			internal_hash_code_set: internal_hash_code = v
		end
	
invariant
	extendible: Extendible
	compare_character: not object_comparison

		-- from READABLE_STRING_32
	area_not_void: area /= Void

		-- from COMPARABLE
	irreflexive_comparison: not (Current < Current)

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

		-- from READABLE_INDEXABLE
	consistent_boundaries: Lower <= count or else Lower = count + 1

		-- from STRING_GENERAL
	mutable: not is_immutable

		-- 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)

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 STRING_32