note
	description: "[
		Sequences of immutable 8-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: 2020-05-12 20:58:01 +0000 (Tue, 12 May 2020) $"
	revision: "$Revision: 104181 $"

frozen class interface
	IMMUTABLE_STRING_8

create 
	make (n: INTEGER_32)
			-- Allocate space for at least n characters.
			-- (from READABLE_STRING_8)
		require -- from READABLE_STRING_GENERAL
			non_negative_size: n >= 0
		ensure -- from READABLE_STRING_GENERAL
			empty_string: count = 0
			area_allocated: capacity >= n

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

	make_filled (c: CHARACTER_8; n: INTEGER_32)
			-- Create string of length n filled with c.
			-- (from READABLE_STRING_8)
		require -- from READABLE_STRING_8
			valid_count: n >= 0
		ensure -- from READABLE_STRING_8
			count_set: count = n
			area_allocated: capacity >= n
			filled: occurrences (c) = count

	make_from_string (s: READABLE_STRING_8)
			-- Initialize from the characters of s.
			-- (from READABLE_STRING_8)
		require -- from READABLE_STRING_8
			string_exists: s /= Void
		ensure -- from READABLE_STRING_8
			not_shared_implementation: Current /= s implies not shared_with (s)
			initialized: same_string (s)

	make_from_c (c_string: POINTER)
			-- Initialize from contents of c_string,
			-- a string created by some C function.
			-- (from READABLE_STRING_8)
		require -- from READABLE_STRING_8
			c_string_exists: c_string /= default_pointer

	make_from_c_substring (c_string: POINTER; start_pos, end_pos: INTEGER_32)
			-- Initialize from substring of c_string,
			-- between start_pos and end_pos,
			-- c_string created by some C function.
			-- (from READABLE_STRING_8)
		require -- from READABLE_STRING_8
			c_string_exists: c_string /= default_pointer
			start_position_big_enough: start_pos >= 1
			end_position_big_enough: start_pos <= end_pos + 1

	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 1 single byte.
			-- ex: (char*) "abc"  for STRING_8 "abc"			
			-- (from READABLE_STRING_8)
		require -- from READABLE_STRING_8
			a_byte_array_exists: not a_byte_array.is_default_pointer

	make_from_cil (a_system_string: SYSTEM_STRING)
			-- Initialize Current with a_system_string.
		require -- from READABLE_STRING_8
			is_dotnet: {PLATFORM}.is_dotnet

	make_from_separate (other: separate READABLE_STRING_8)
			-- Initialize current string from other.
			-- (from READABLE_STRING_8)
		require -- from READABLE_STRING_8
			other_not_void: other /= Void
		ensure -- from READABLE_STRING_8
			same_string: 


create {IMMUTABLE_STRING_8}
	make_from_area_and_bounds (a: like area; low, n: like count)
			-- Initialize current with area a with lower bounds low and count n.
		require
			a_not_void: a /= Void
			a_valid_count: (a.count - low) >= count + 1
			low_non_negative: low >= 0
			n_non_negative: n >= 0
		ensure
			area_set: area = a
			area_lower_set: area_lower = low
			count_set: count = n

convert
	make_from_area_and_bounds ({READABLE_STRING_8,
		STRING_8}),
	make_from_area_and_bounds ({SYSTEM_STRING}),
	make_from_area_and_bounds: {SYSTEM_STRING},
	make_from_area_and_bounds: {READABLE_STRING_32},
	make_from_area_and_bounds: {STRING_32},
	make_from_area_and_bounds: {STRING_8}

feature -- Access

	at alias "@" (i: INTEGER_32): CHARACTER_8
			-- Character at position i.
			-- Was declared in IMMUTABLE_STRING_8 as synonym of item.

	case_insensitive_hash_code: INTEGER_32
			-- Hash code value of the lower case version of Current.
			-- (from READABLE_STRING_GENERAL)
		ensure -- from READABLE_STRING_GENERAL
			consistent: Result = as_lower.case_insensitive_hash_code

	character_32_item (i: INTEGER_32): CHARACTER_32
			-- Character at position i.
		require -- from READABLE_STRING_GENERAL
			valid_index: valid_index (i)

	code (i: INTEGER_32): NATURAL_32
			-- Numeric code of character at position i.
		require -- from READABLE_STRING_GENERAL
			valid_index: valid_index (i)

	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_8)
		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

	generating_type: TYPE [detachable IMMUTABLE_STRING_8]
			-- Type of current object
			-- (type of which it is a direct instance)
			-- (from ANY)
		ensure -- from ANY
			generating_type_not_void: Result /= Void

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

	hash_code: INTEGER_32
			-- Hash code value
			-- (from READABLE_STRING_GENERAL)
		ensure -- from HASHABLE
			good_hash_value: Result >= 0

	character_32_index_of (c: like character_32_item; 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
		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).character_32_has (c)
			found_if_present: substring (start_index, count).character_32_has (c) implies character_32_item (Result) = c
			none_before: substring (start_index, count).character_32_has (c) implies not substring (start_index, Result - 1).character_32_has (c)

	index_of (c: CHARACTER_8; start_index: INTEGER_32): INTEGER_32
			-- Position of first occurrence of c at or after start_index;
			-- 0 if none.
			-- (from READABLE_STRING_8)
		require -- from READABLE_STRING_8
			start_large_enough: start_index >= 1
			start_small_enough: start_index <= count + 1
		ensure -- from READABLE_STRING_8
			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)

	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
		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)

	item alias "[]" (i: INTEGER_32): CHARACTER_8
			-- Character at position i.
			-- Was declared in IMMUTABLE_STRING_8 as synonym of at.
		require -- from READABLE_INDEXABLE
			valid_index: valid_index (i)

	item_code (i: INTEGER_32): INTEGER_32
			-- Numeric code of character at position i.
			-- Use code instead for consistency with Unicode handling.
		require -- from READABLE_STRING_8
			index_small_enough: i <= count
			index_large_enough: i > 0

	last_index_of (c: CHARACTER_8; start_index_from_end: INTEGER_32): INTEGER_32
			-- Position of last occurrence of c,
			-- 0 if none.
			-- (from READABLE_STRING_8)
		require -- from READABLE_STRING_8
			start_index_small_enough: start_index_from_end <= count
			start_index_large_enough: start_index_from_end >= 1
		ensure -- from READABLE_STRING_8
			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)

	character_32_last_index_of (c: like character_32_item; 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
		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).character_32_has (c)
			found_if_present: substring (1, start_index_from_end).character_32_has (c) implies character_32_item (Result) = c
			none_after: substring (1, start_index_from_end).character_32_has (c) implies not substring (Result + 1, start_index_from_end).character_32_has (c)

	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
		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)

	new_cursor: STRING_8_ITERATION_CURSOR
			-- Fresh cursor associated with current structure
			-- (from READABLE_STRING_8)
		require -- from  ITERABLE
			True
		ensure -- from ITERABLE
			result_attached: Result /= Void

	shared_with (other: READABLE_STRING_8): BOOLEAN
			-- Does string share the text of other?
			-- (from READABLE_STRING_8)

	string: STRING_8
			-- New STRING_8 having same character sequence as Current.
			-- (from READABLE_STRING_8)
		ensure -- from READABLE_STRING_8
			string_not_void: Result /= Void
			string_type: Result.same_type (create {STRING_8}.make_empty)
			first_item: count > 0 implies Result.item (1) = item (1)
			recurse: count > 1 implies Result.substring (2, count) ~ substring (2, count).string

	string_representation: STRING_8
			-- Similar to string but only create a new object if Current is not of dynamic type STRING_8.
			-- (from READABLE_STRING_8)
		ensure -- from READABLE_STRING_8
			result_not_void: Result /= Void
			correct_type: Result.same_type (create {STRING_8}.make_empty)
			first_item: count > 0 implies Result.item (1) = item (1)
			recurse: count > 1 implies Result.substring (2, count) ~ substring (2, count).string

	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_8)
		require -- from READABLE_STRING_GENERAL
			other_not_void: other /= Void
			valid_start_index: start_index >= 1 and start_index <= count + 1
		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)

	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_8)
		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
		ensure -- from READABLE_STRING_GENERAL
			correct_place: Result > 0 implies other.same_string (substring (Result, Result + other.count - 1))

	True_constant: STRING_8 = "true"
			-- Constant string "true"
			-- (from READABLE_STRING_GENERAL)
	
feature -- Measurement

	capacity: INTEGER_32
			-- Number of characters allocated in Current
			-- (from READABLE_STRING_8)
		require -- from  READABLE_STRING_GENERAL
			True
		ensure -- from READABLE_STRING_GENERAL
			capacity_non_negative: Result >= 0

	count: INTEGER_32
			-- Actual number of characters making up the string.
			-- (from READABLE_STRING_8)

	Lower: INTEGER_32 = 1
			-- Minimum index.
			-- (from READABLE_STRING_8)

	occurrences (c: CHARACTER_8): INTEGER_32
			-- Number of times c appears in the string.
			-- (from READABLE_STRING_8)
		ensure then -- from READABLE_STRING_8
			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)

	character_32_occurrences (c: CHARACTER_32): INTEGER_32
			-- Number of times c appears in the string
			-- (from READABLE_STRING_GENERAL)
		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 character_32_item (1) /= c) implies Result = substring (2, count).character_32_occurrences (c)
			recurse_if_found_at_first_position: (count > 0 and then character_32_item (1) = c) implies Result = 1 + substring (2, count).character_32_occurrences (c)
	
feature -- Comparison

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

	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
		ensure -- from READABLE_STRING_GENERAL
			definition: Result = s.same_string (substring (count - s.count + 1, count))

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

	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
		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))

	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)
		ensure -- from READABLE_STRING_GENERAL
			symmetric: Result implies other.is_case_insensitive_equal (Current)
			consistent: attached {IMMUTABLE_STRING_8} other as l_other implies (standard_is_equal (l_other) implies Result)
			valid_result: as_lower ~ other.as_lower implies Result

	is_case_insensitive_equal (other: READABLE_STRING_8): BOOLEAN
			-- Is string made of same character sequence as other regardless of casing
			-- (possibly with a different capacity)?
			-- (from READABLE_STRING_8)
		require -- from READABLE_STRING_8
			other_not_void: other /= Void
		ensure -- from READABLE_STRING_8
			symmetric: Result implies other.is_case_insensitive_equal (Current)
			consistent: attached {IMMUTABLE_STRING_8} other as l_other implies (standard_is_equal (l_other) implies Result)
			valid_result: as_lower.same_string (other.as_lower) implies Result

	frozen is_deep_equal alias "≡≡≡" (other: IMMUTABLE_STRING_8): BOOLEAN
			-- Are Current and other attached to isomorphic object structures?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			shallow_implies_deep: standard_is_equal (other) implies Result
			same_type: Result implies same_type (other)
			symmetric: Result implies other.is_deep_equal (Current)

	is_equal (other: IMMUTABLE_STRING_8): BOOLEAN
			-- Is string made of same character sequence as other
			-- (possibly with a different capacity)?
			-- (from READABLE_STRING_8)
		require -- from ANY
			other_not_void: other /= Void
		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))

	is_greater alias ">" (other: IMMUTABLE_STRING_8): BOOLEAN
			-- Is current object greater than other?
			-- (from COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		ensure then -- from COMPARABLE
			definition: Result = (other < Current)

	is_greater_equal alias ">=" alias "≥" (other: IMMUTABLE_STRING_8): BOOLEAN
			-- Is current object greater than or equal to other?
			-- (from COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		ensure then -- from COMPARABLE
			definition: Result = (other <= Current)

	is_less alias "<" (other: IMMUTABLE_STRING_8): BOOLEAN
			-- Is string lexicographically lower than other?
			-- (from READABLE_STRING_8)
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		ensure then -- from COMPARABLE
			asymmetric: Result implies not (other < Current)

	is_less_equal alias "<=" alias "≤" (other: IMMUTABLE_STRING_8): BOOLEAN
			-- Is current object less than or equal to other?
			-- (from COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		ensure then -- from COMPARABLE
			definition: Result = ((Current < other) or (Current ~ other))

	max alias "∨" (other: IMMUTABLE_STRING_8): IMMUTABLE_STRING_8
			-- The greater of current object and other
			-- (from COMPARABLE)
		require -- from COMPARABLE
			other_exists: other /= Void
		ensure -- from COMPARABLE
			current_if_not_smaller: Current >= other implies Result = Current
			other_if_smaller: Current < other implies Result = other

	min alias "∧" (other: IMMUTABLE_STRING_8): IMMUTABLE_STRING_8
			-- The smaller of current object and other
			-- (from COMPARABLE)
		require -- from COMPARABLE
			other_exists: other /= Void
		ensure -- from COMPARABLE
			current_if_not_greater: Current <= other implies Result = Current
			other_if_greater: Current > other implies Result = other

	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)
		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))

	same_caseless_characters (other: READABLE_STRING_8; 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_8)
		require -- from READABLE_STRING_8
			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)
		ensure -- from READABLE_STRING_8
			same_characters: Result = substring (index_pos, index_pos + end_pos - start_pos).is_case_insensitive_equal (other.substring (start_pos, end_pos))

	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)
		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))

	same_characters (other: READABLE_STRING_8; 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_8)
		require -- from READABLE_STRING_8
			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)
		ensure -- from READABLE_STRING_8
			same_characters: Result = substring (index_pos, index_pos + end_pos - start_pos).same_string (other.substring (start_pos, end_pos))

	same_string (other: READABLE_STRING_8): BOOLEAN
			-- Do Current and other have same character sequence?
			-- (from READABLE_STRING_8)
		require -- from READABLE_STRING_8
			other_not_void: other /= Void
		ensure -- from READABLE_STRING_8
			definition: Result = (string ~ other.string)

	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

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

	frozen standard_is_equal alias "≜" (other: IMMUTABLE_STRING_8): BOOLEAN
			-- Is other attached to an object of the same type
			-- as current object, and field-by-field identical to it?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			same_type: Result implies same_type (other)
			symmetric: Result implies other.standard_is_equal (Current)

	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
		ensure -- from READABLE_STRING_GENERAL
			definition: Result = s.same_string (substring (1, s.count))

	three_way_comparison alias "⋚" (other: IMMUTABLE_STRING_8): INTEGER_32
			-- If current object equal to other, 0;
			-- if smaller, -1; if greater, 1
			-- (from COMPARABLE)
		require -- from COMPARABLE
			other_exists: other /= Void
		ensure -- from COMPARABLE
			equal_zero: (Result = 0) = (Current ~ other)
			smaller_negative: (Result = -1) = (Current < other)
			greater_positive: (Result = 1) = (Current > other)
	
feature -- Status report

	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

	ends_with (s: READABLE_STRING_8): BOOLEAN
			-- Does string finish with s?
			-- (from READABLE_STRING_8)
		require -- from READABLE_STRING_8
			argument_not_void: s /= Void
		ensure -- from READABLE_STRING_8
			definition: Result = s.same_string (substring (count - s.count + 1, count))

	character_32_has (c: like character_32_item): BOOLEAN
			-- Does string include c?
			-- (from READABLE_STRING_GENERAL)
		ensure then -- from READABLE_STRING_GENERAL
			false_if_empty: count = 0 implies not Result
			true_if_first: count > 0 and then character_32_item (1) = c implies Result
			recurse: (count > 0 and then character_32_item (1) /= c) implies (Result = substring (2, count).character_32_has (c))

	has (c: CHARACTER_8): BOOLEAN
			-- Does string include c?
			-- (from READABLE_STRING_8)
		ensure -- from READABLE_STRING_8
			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))

	has_code (c: like code): BOOLEAN
			-- Does string include c?
			-- (from READABLE_STRING_GENERAL)
		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))

	is_boolean: BOOLEAN
			-- Does Current represent a BOOLEAN?
			-- (from READABLE_STRING_8)
		require -- from  READABLE_STRING_GENERAL
			True
		ensure -- from READABLE_STRING_GENERAL
			is_boolean: Result = (True_constant.same_string_general (as_lower) or False_constant.same_string_general (as_lower))

	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)

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

	Is_immutable: BOOLEAN = True
			-- Can the character sequence of Current be not changed?
			-- (from IMMUTABLE_STRING_GENERAL)

	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)

	is_integer_16: BOOLEAN
			-- Does Current represent an INTEGER_16?
			-- (from READABLE_STRING_GENERAL)

	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)

	is_integer_64: BOOLEAN
			-- Does Current represent an INTEGER_64?
			-- (from READABLE_STRING_GENERAL)

	is_integer_8: BOOLEAN
			-- Does Current represent an INTEGER_8?
			-- (from READABLE_STRING_GENERAL)

	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)

	is_natural_16: BOOLEAN
			-- Does Current represent a NATURAL_16?
			-- (from READABLE_STRING_GENERAL)

	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)

	is_natural_64: BOOLEAN
			-- Does Current represent a NATURAL_64?
			-- (from READABLE_STRING_GENERAL)

	is_natural_8: BOOLEAN
			-- Does Current represent a NATURAL_8?
			-- (from READABLE_STRING_GENERAL)

	is_number_sequence: BOOLEAN
			-- Does Current represent a number sequence?
			-- (from READABLE_STRING_GENERAL)

	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)

	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)

	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)

	is_real_sequence: BOOLEAN
			-- Does Current represent a real sequence?
			-- (from READABLE_STRING_GENERAL)

	Is_string_32: BOOLEAN = False
			-- Is Current a sequence of CHARACTER_32?
			-- (from READABLE_STRING_8)

	Is_string_8: BOOLEAN = True
			-- Is Current a sequence of CHARACTER_8?
			-- (from READABLE_STRING_8)

	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_8)
		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

	Is_valid_as_string_8: BOOLEAN = True
			-- Is Current convertible to a sequence of CHARACTER_8 without information loss?
			-- (from READABLE_STRING_8)

	is_whitespace: BOOLEAN
			-- Is structure containing only whitespace characters?
			-- (from READABLE_STRING_GENERAL)

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

	starts_with (s: READABLE_STRING_8): BOOLEAN
			-- Does string begin with s?
			-- (from READABLE_STRING_8)
		require -- from READABLE_STRING_8
			argument_not_void: s /= Void
		ensure -- from READABLE_STRING_8
			definition: Result = s.same_string (substring (1, s.count))

	valid_code (v: NATURAL_32): BOOLEAN
			-- Is v a valid code for a CHARACTER_32?
			-- (from READABLE_STRING_8)
		require -- from  READABLE_STRING_GENERAL
			True

	valid_index (i: INTEGER_32): BOOLEAN
			-- Is i within the bounds of the string?
			-- (from READABLE_STRING_GENERAL)
		require -- from  READABLE_INDEXABLE
			True
		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)
	
feature -- Conversion

	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)
		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)

	split (a_separator: CHARACTER_32): LIST [IMMUTABLE_STRING_8]
			-- Split on a_separator.
			-- (from READABLE_STRING_GENERAL)
		ensure -- from READABLE_STRING_GENERAL
				Result /= Void

	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
		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))

	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
		ensure -- from READABLE_STRING_GENERAL
			to_cil_not_void: Result /= Void

	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

	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

	to_integer_16: INTEGER_16
			-- 16-bit integer value
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_integer_16: is_integer_16

	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

	to_integer_64: INTEGER_64
			-- 64-bit integer value
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_integer_64: is_integer_64

	to_integer_8: INTEGER_8
			-- 8-bit integer value
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_integer_8: is_integer_8

	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

	to_natural_16: NATURAL_16
			-- 16-bit natural value
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_natural_16: is_natural_16

	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

	to_natural_64: NATURAL_64
			-- 64-bit natural value
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_natural_64: is_natural_64

	to_natural_8: NATURAL_8
			-- 8-bit natural value
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			is_natural_8: is_natural_8

	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

	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

	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

	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)
		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)

	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
		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)
	
feature -- Duplication

	copy (other: like Current)
			-- Reinitialize by copying the characters of other.
			-- (This is also used by twin.)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		ensure -- from ANY
			is_equal: Current ~ other
		ensure then -- from READABLE_STRING_8
			new_result_count: count = other.count
		ensure then
			new_result_count: count = other.count

	frozen deep_copy (other: IMMUTABLE_STRING_8)
			-- Effect equivalent to that of:
			--		copy (other . deep_twin)
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			deep_equal: deep_equal (Current, other)

	frozen deep_twin: IMMUTABLE_STRING_8
			-- New object structure recursively duplicated from Current.
			-- (from ANY)
		ensure -- from ANY
			deep_twin_not_void: Result /= Void
			deep_equal: deep_equal (Current, Result)

	head (n: INTEGER_32): IMMUTABLE_STRING_8
			-- Prefix, retaining first n characters (or as many as available).
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			non_negative_argument: n >= 0
		ensure -- from READABLE_STRING_GENERAL
			same_count: count = old count
			new_count: Result.count = n.min (count)

	frozen standard_copy (other: IMMUTABLE_STRING_8)
			-- Copy every field of other onto corresponding field
			-- of current object.
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		ensure -- from ANY
			is_standard_equal: standard_is_equal (other)

	frozen standard_twin: IMMUTABLE_STRING_8
			-- New object field-by-field identical to other.
			-- Always uses default copying semantics.
			-- (from ANY)
		ensure -- from ANY
			standard_twin_not_void: Result /= Void
			equal: standard_equal (Result, Current)

	tail (n: INTEGER_32): IMMUTABLE_STRING_8
			-- Suffix, retaining last n characters (or as many as available).
			-- (from READABLE_STRING_GENERAL)
		require -- from READABLE_STRING_GENERAL
			non_negative_argument: n >= 0
		ensure -- from READABLE_STRING_GENERAL
			same_count: count = old count
			new_count: Result.count = n.min (count)

	frozen twin: IMMUTABLE_STRING_8
			-- New object equal to Current
			-- twin calls copy; to change copying/twinning semantics, redefine copy.
			-- (from ANY)
		ensure -- from ANY
			twin_not_void: Result /= Void
			is_equal: Result ~ Current
	
feature -- Basic operations

	as_lower: like Current
			-- New object with all letters in lower case.
		ensure -- from READABLE_STRING_GENERAL
			as_lower_attached: Result /= Void
			length: Result.count = count
			anchor: count > 0 implies Result.character_32_item (1) = character_32_item (1).as_lower
			recurse: count > 1 implies Result.substring (2, count) ~ substring (2, count).as_lower

	as_upper: like Current
			-- New object with all letters in upper case
		ensure -- from READABLE_STRING_GENERAL
			as_upper_attached: Result /= Void
			length: Result.count = count
			anchor: count > 0 implies Result.character_32_item (1) = character_32_item (1).as_upper
			recurse: count > 1 implies Result.substring (2, count) ~ substring (2, count).as_upper

	frozen default: detachable IMMUTABLE_STRING_8
			-- Default value of object's type
			-- (from ANY)

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

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

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

	is_empty: BOOLEAN
			-- Is structure empty?

	linear_representation: LINEAR [CHARACTER_8]
			-- Representation as a linear structure

	mirrored: like Current
			-- Mirror image of string;
			-- Result for "Hello world" is "dlrow olleH".
		ensure -- from READABLE_STRING_8
			same_count: Result.count = count

	plus alias "+" (s: READABLE_STRING_8): like Current
			-- Concatenation with s.
		require -- from READABLE_STRING_8
			argument_attached: attached s
		ensure -- from READABLE_STRING_8
			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)

	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
		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)

	shared_substring (start_index, end_index: INTEGER_32): like Current

	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
		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.character_32_item (1) = character_32_item (start_index)
			recurse: Result.count > 0 implies Result.substring (2, Result.count) ~ substring (start_index + 1, end_index)
	
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)
	
feature -- Output

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

	out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from READABLE_STRING_8)
		require -- from  ANY
			True
		ensure -- from ANY
			out_not_void: Result /= Void
		ensure then -- from READABLE_STRING_8
			out_not_void: Result /= Void
			same_items: same_type ("") implies Result.same_string_general (Current)

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

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

	Operating_environment: OPERATING_ENVIRONMENT
			-- Objects available from the operating system
			-- (from ANY)
		ensure -- from ANY
			instance_free: class
			operating_environment_not_void: Result /= Void
	
invariant
		-- from READABLE_STRING_8
	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 IMMUTABLE_STRING_GENERAL
	immutable: Is_immutable

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 IMMUTABLE_STRING_8

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