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indexing
	status: "See notice at end of class"
	date: "$Date: 2001/11/16 20:34:14 $"
	revision: "$Revision: 1.1.1.1 $"

class 
	SEQ_STRING

create 
	make

feature {NONE} -- Initialization

	make (n: INTEGER) is
			-- Allocate space for at least n characters.
			-- (from STRING)
		require -- from STRING
			non_negative_size: n >= 0
		do
			count := 0
			if n = 0 then
				area := empty_area
			else
				make_area (n + 1)
			end
		ensure -- from STRING
			empty_string: count = 0
			area_allocated: capacity >= n
		end

	make_area (n: INTEGER) is
			-- Creates a special object for n entries.
			-- (from TO_SPECIAL)
		require -- from TO_SPECIAL
			non_negative_argument: n >= 0
		do
			create area.make (n)
		ensure -- from TO_SPECIAL
			area_allocated: area /= void and then area.count = n
		end
	
feature -- Initialization

	adapt (s: STRING): like Current is
			-- Object of a type conforming to the type of s,
			-- initialized with attributes from s
			-- (from STRING)
		do
			create Result.make (0)
			Result.string_share (s)
		end

	from_c (c_string: POINTER) is
			-- Reset contents of string from contents of c_string,
			-- a string created by some external C function.
			-- (from STRING)
		require -- from STRING
			c_string_exists: c_string /= default_pointer
		local
			length: INTEGER
		do
			length := str_len (c_string)
			if capacity < length then
				make_area (length + 1)
			end;
			($area).memory_copy (c_string, length)
			count := length
		ensure -- from STRING
			no_zero_byte: not has ('%U')
		end

	from_c_substring (c_string: POINTER; start_pos, end_pos: INTEGER) is
			-- Reset contents of string from substring of c_string,
			-- a string created by some external C function.
			-- (from STRING)
		require -- from STRING
			c_string_exists: c_string /= default_pointer
			start_position_big_enough: start_pos >= 1
			end_position_big_enough: start_pos <= end_pos + 1
		local
			length: INTEGER
		do
			length := end_pos - start_pos + 1
			if capacity < length then
				make_area (length + 1)
			end;
			($area).memory_copy (c_string + (start_pos - 1), (end_pos - start_pos + 1))
			count := length
		ensure -- from STRING
			valid_count: count = end_pos - start_pos + 1
		end

	make_from_c (c_string: POINTER) is
			-- Initialize from contents of c_string,
			-- a string created by some external C function
			-- (from STRING)
		require -- from STRING
			c_string_exists: c_string /= default_pointer
		local
			length: INTEGER
		do
			length := str_len (c_string)
			make_area (length + 1);
			($area).memory_copy (c_string, length)
			count := length
		end

	make_from_string (s: STRING) is
			-- Initialize from the characters of s.
			-- (Useful in proper descendants of class STRING,
			-- to initialize a string-like object from a manifest string.)
			-- (from STRING)
		require -- from STRING
			string_exists: s /= void
		do
			area := s.area
			count := s.count
		ensure -- from STRING
			shared_implementation: shared_with (s)
		end

	remake (n: INTEGER) is
		obsolete "Use `make' instead"
			-- Allocate space for at least n characters.
			-- (from STRING)
		require -- from STRING
			non_negative_size: n >= 0
		do
			count := 0
			make (n)
		ensure -- from STRING
			empty_string: count = 0
			area_allocated: capacity >= n
		end
	
feature -- Access

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

	current_item: CHARACTER is
			-- Current item
		require -- from TRAVERSABLE
			not_off: not off
		require -- from ACTIVE
			readable: readable
		do
			Result := item (index)
		end

	False_constant: STRING is "false"
			-- Constant string "false"
			-- (from STRING)

	fuzzy_index (other: STRING; start: INTEGER; fuzz: INTEGER): INTEGER is
			-- 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 STRING)
		require -- from STRING
			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
		local
			a: ANY
		do
			a := other.area
			Result := str_str ($area, $a, count, other.count, start, fuzz)
		end

	has (c: CHARACTER): BOOLEAN is
			-- Does string include c?
		do
			if not is_empty then
				Result := (index_of (c, 1) /= 0)
			end
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty
		end

	hash_code: INTEGER is
			-- Hash code value
			-- (from STRING)
		do
			Result := hashcode ($area, count)
		ensure -- from HASHABLE
			good_hash_value: Result >= 0
		end

	index: INTEGER
			-- Index of current_item, if valid
			-- Valid values are between 1 and count (if count > 0).

	index_of (c: CHARACTER; start: INTEGER): INTEGER is
			-- Position of first occurrence of c at or after start;
			-- 0 if none.
			-- (from STRING)
		require -- from STRING
			start_large_enough: start >= 1
			start_small_enough: start <= count + 1
		local
			a: like area
			i, nb: INTEGER
		do
			nb := count
			if start <= nb then
				from
					i := start - 1
					nb := nb - 1
					a := area
				until
					i > nb or else a.item (i) = c
				loop
					i := i + 1
				end
				if i <= nb then
					Result := i + 1
				end
			end
		ensure -- from STRING
			correct_place: Result > 0 implies item (Result) = c
		end

	index_of_occurrence (c: CHARACTER; i: INTEGER): INTEGER is
			-- Index of i-th occurrence of c.
			-- 0 if none.
		require -- from LINEAR
			positive_occurrences: i > 0
		local
			occur: INTEGER
		do
			if not is_empty then
				from
					Result := index_of (c, 1)
					if Result /= 0 then
						occur := 1
					end
				until
					(Result = 0) or else (occur = i)
				loop
					if Result /= count then
						Result := index_of (c, Result + 1)
						if Result /= 0 then
							occur := occur + 1
						end
					else
						Result := 0
					end
				end
			end
		ensure -- from LINEAR
			non_negative_result: Result >= 0
		ensure then
			index_value: (Result = 0) or item (Result) = c
		end

	item (i: INTEGER): CHARACTER is
			-- Character at position i
			-- Was declared in STRING as synonym of @.
			-- (from STRING)
		require -- from TABLE
			valid_key: valid_index (k)
		do
			Result := area.item (i - 1)
		end

	item_code (i: INTEGER): INTEGER is
			-- Numeric code of character at position i
			-- (from STRING)
		require -- from STRING
			index_small_enough: i <= count
			index_large_enough: i > 0
		do
			Result := area.item (i - 1).code
		end

	last_index_of (c: CHARACTER; start_index_from_end: INTEGER): INTEGER is
			-- Position of last occurence of c.
			-- 0 if none
			-- (from STRING)
		require -- from STRING
			start_index_small_enough: start_index_from_end <= count
			start_index_large_enough: start_index_from_end >= 1
		local
			a: like area
			i: INTEGER
		do
			from
				i := start_index_from_end - 1
				a := area
			until
				i < 0 or else a.item (i) = c
			loop
				i := i - 1
			end
			if i >= 0 then
				Result := i + 1
			end
		ensure -- from STRING
			correct_place: Result > 0 implies item (Result) = c
		end

	off: BOOLEAN is
			-- Is there no current item?
			-- (from BILINEAR)
		do
			Result := before or after
		end

	search_after (c: CHARACTER) is
			-- Move cursor to first position
			-- (at or after current cursor position)
			-- where current_item and c are identical.
		do
			if not off then
				index := index_of (c, index)
				if index = 0 then
					index := count + 1
				end
			end
		end

	search_before (c: CHARACTER) is
			-- Move cursor to greatest position at or before cursor
			-- where current_item and c are identical;
			-- go before if unsuccessful.
		local
			str: like Current
		do
			str := mirrored
			if not str.off then
				index := count + 1 - str.index_of (c, str.index)
				if index = count + 1 then
					index := 0
				end
			end
		end

	search_string_after (s: STRING; fuzzy: INTEGER) is
			-- Move cursor to first position
			-- (at or after cursor position) where `substring
			-- (index, index + s.count)' and s are identical.
			-- Go after if unsuccessful.
			-- The 'fuzzy' parameter is the maximum allowed number
			-- of mismatches within the pattern. A 0 means an exact match.
		local
			s_area: ANY
		do
			if not off then
				s_area := s.area
				index := str_str ($area, $s_area, count, s.count, index, fuzzy)
				if index = 0 then
					index := count + 1
				end
			end
		end

	search_string_before (s: STRING; fuzzy: INTEGER) is
			-- Move cursor to first position
			-- (at or before cursor position) where `substring
			-- (index, index + s.count)' and s are identical.
			-- Go before if unsuccessful.
			-- The 'fuzzy' parameter is the maximum allowed number
			-- of mismatches within the pattern. A 0 means an exact match.
		local
			s_mir_area, mir_area: ANY
			str_mirrored: like Current
			s_mirrored: STRING
		do
			if not off then
				str_mirrored := mirrored
				s_mirrored := s.mirrored
				s_mir_area := s_mirrored.area
				mir_area := str_mirrored.area
				index := count - str_str ($mir_area, $s_mir_area, count, s.count, str_mirrored.index, fuzzy) + 1
				if index = count + 1 then
					index := 0
				else
					index := index - s.count + 1
				end
			end
		end

	shared_with (other: like Current): BOOLEAN is
			-- Does string share the text of other?
			-- (from STRING)
		do
			Result := (other /= void) and then (area = other.area)
		end

	substring_index (other: STRING; start: INTEGER): INTEGER is
			-- Position of first occurrence of other at or after start;
			-- 0 if none.
			-- (from STRING)
		require -- from STRING
			other_nonvoid: other /= void
			other_notempty: not other.is_empty
			start_large_enough: start >= 1
			start_small_enough: start <= count
		local
			a: ANY
		do
			a := other.area
			Result := str_str ($area, $a, count, other.count, start, 0)
		ensure -- from STRING
			correct_place: Result > 0 implies substring (Result, Result + other.count - 1).is_equal (other)
		end

	True_constant: STRING is "true"
			-- Constant string "true"
			-- (from STRING)

	infix "@" (i: INTEGER): CHARACTER is
			-- Character at position i
			-- Was declared in STRING as synonym of item.
			-- (from STRING)
		require -- from TABLE
			valid_key: valid_index (k)
		do
			Result := area.item (i - 1)
		end
	
feature {NONE} -- Access

	sequential_search (v: like current_item) is
			-- Move to first position (at or after current
			-- position) where item and v are equal.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- If no such position ensure that exhausted will be true.
			-- (from LINEAR)
		do
			if object_comparison and v /= void then
				from
				until
					exhausted or else (current_item /= void and then v.is_equal (current_item))
				loop
					forth
				end
			else
				from
				until
					exhausted or else v = current_item
				loop
					forth
				end
			end
		ensure -- from LINEAR
			object_found: (not exhausted and object_comparison) implies equal (v, current_item)
			item_found: (not exhausted and not object_comparison) implies v = current_item
		end
	
feature -- Measurement

	additional_space: INTEGER is
			-- Proposed number of additional items
			-- (from RESIZABLE)
		do
			Result := (capacity * growth_percentage // 100).max (minimal_increase)
		ensure -- from RESIZABLE
			at_least_one: Result >= 1
		end

	capacity: INTEGER is
			-- Allocated space
			-- (from STRING)
		do
			Result := area.count - 1
		end

	count: INTEGER
			-- Actual number of characters making up the string
			-- (from STRING)

	Growth_percentage: INTEGER is 50
			-- Percentage by which structure will grow automatically
			-- (from RESIZABLE)

	index_set: INTEGER_INTERVAL is
			-- Range of acceptable indexes
			-- (from STRING)
		do
			create Result.make (1, count)
		ensure -- from INDEXABLE
			not_void: Result /= void
		ensure then -- from STRING
			Result.count = count
		end

	Minimal_increase: INTEGER is 5
			-- Minimal number of additional items
			-- (from RESIZABLE)

	occurrences (c: CHARACTER): INTEGER is
			-- Number of times c appears in the string
			-- (from STRING)
		local
			counter, nb: INTEGER
			a: SPECIAL [CHARACTER]
		do
			from
				counter := 0
				nb := count - 1
				a := area
			until
				counter > nb
			loop
				if a.item (counter) = c then
					Result := Result + 1
				end
				counter := counter + 1
			end
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
		end
	
feature -- Comparison

	is_equal (other: like Current): BOOLEAN is
			-- Is string made of same character sequence as other
			-- (possibly with a different capacity)?
			-- (from STRING)
		require -- from ANY
			other_not_void: other /= void
		local
			o_area: like area
		do
			if other = Current then
				Result := True
			elseif count = other.count then
				o_area := other.area;
				Result := str_strict_cmp ($area, $o_area, count) = 0
			end
		ensure -- from ANY
			symmetric: Result implies other.is_equal (Current)
			consistent: standard_is_equal (other) implies Result
		ensure then -- from COMPARABLE
			trichotomy: Result = (not (Current < other) and not (other < Current))
		end

	max (other: like Current): like Current is
			-- 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 (other: like Current): like Current is
			-- 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

	three_way_comparison (other: like Current): INTEGER is
			-- 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) = is_equal (other)
			smaller_negative: (Result = - 1) = (Current < other)
			greater_positive: (Result = 1) = (Current > other)
		end

	infix "<" (other: like Current): BOOLEAN is
			-- Is string lexicographically lower than other?
			-- (from STRING)
		require -- from PART_COMPARABLE
			other_exists: other /= void
		local
			other_area: like area
			other_count: INTEGER
			current_count: INTEGER
		do
			other_area := other.area
			other_count := other.count
			current_count := count
			if other_count = current_count then
				Result := str_strict_cmp ($other_area, $area, other_count) > 0
			else
				if current_count < other_count then
					Result := str_strict_cmp ($other_area, $area, current_count) >= 0
				else
					Result := str_strict_cmp ($other_area, $area, other_count) > 0
				end
			end
		ensure then -- from COMPARABLE
			asymmetric: Result implies not (other < Current)
		end

	infix "<=" (other: like Current): BOOLEAN is
			-- 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 is_equal (other))
		end

	infix ">" (other: like Current): BOOLEAN is
			-- 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

	infix ">=" (other: like Current): BOOLEAN is
			-- 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
	
feature -- Status report

	after: BOOLEAN is
			-- Is there no valid cursor position to the right of cursor?
		do
			Result := index > count
		end

	before: BOOLEAN is
			-- Is there no valid cursor position to the left of cursor?
		do
			Result := index < 1
		end

	Changeable_comparison_criterion: BOOLEAN is False
			-- (from STRING)

	empty: BOOLEAN is
		obsolete "ELKS 2000: Use `is_empty' instead"
			-- Is there no element?
			-- (from CONTAINER)
		do
			Result := is_empty
		end

	exhausted: BOOLEAN is
			-- Has structure been completely explored?
			-- (from LINEAR)
		do
			Result := off
		ensure -- from LINEAR
			exhausted_when_off: off implies Result
		end

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

	full: BOOLEAN is
			-- Is structure full?
			-- (from BOUNDED)
		do
			Result := (