Class STRING

ISE Eiffel 4.5.020

indexing
	description: "Sequences of characters, accessible through integer indices in a contiguous range."
	status: "See notice at end of class"
	date: "$Date: 2002/01/31 11:04:59 $"
	revision: "$Revision: 1.1 $"

class interface
	STRING

create 

	make (n: INTEGER)
		require
			non_negative_size: n >= 0
		ensure
			empty_string: count = 0;
			area_allocated: capacity >= n

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

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

feature -- Initialization

	adapt (s: STRING): like Current
			-- Object of a type conforming to the type of s,
			-- initialized with attributes from s

	from_c (c_string: POINTER)
			-- Reset contents of string from contents of c_string,
			-- a string created by some external C function.
		require
			c_string_exists: c_string /= default_pointer

	from_c_substring (c_string: POINTER; start_pos, end_pos: INTEGER)
			-- Reset contents of string from substring of c_string,
			-- a string created by some external 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
		ensure
			valid_count: count = end_pos - start_pos + 1

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

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

	remake (n: INTEGER)
			-- Allocate space for at least n characters.
		require
			non_negative_size: n >= 0
		ensure
			empty_string: count = 0;
			area_allocated: capacity >= n
	
feature -- Access

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

	False_constant: STRING is "false"
			-- Constant string "false"

	fuzzy_index (other: STRING; start: INTEGER; fuzz: INTEGER): INTEGER
			-- 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
		require
			other_exists: other /= void;
			other_not_empty: not other.empty;
			start_large_enough: start >= 1;
			start_small_enough: start <= count;
			acceptable_fuzzy: fuzz <= other.count

	has (c: CHARACTER): BOOLEAN
			-- Does string include c?
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not empty

	hash_code: INTEGER
			-- Hash code value
		ensure -- from HASHABLE
			good_hash_value: Result >= 0

	index_of (c: CHARACTER; start: INTEGER): INTEGER
			-- Position of first occurrence of c at or after start;
			-- 0 if none.
		require
			start_large_enough: start >= 1;
			start_small_enough: start <= count
		ensure
			correct_place: Result > 0 implies item (Result) = c

	item (i: INTEGER): CHARACTER
			-- Character at position i
			-- Was declared in STRING as synonym of item and @.
		require -- from TABLE
			valid_key: valid_index (k)

	item_code (i: INTEGER): INTEGER
			-- Numeric code of character at position i
		require
			index_small_enough: i <= count;
			index_large_enough: i > 0

	last_index_of (c: CHARACTER; start_index_from_end: INTEGER): INTEGER
			-- Position of last occurence of c.
			-- 0 if none
		require
			start_index_small_enough: start_index_from_end <= count;
			start_index_large_enough: start_index_from_end >= 1
		ensure
			correct_place: Result > 0 implies item (Result) = c

	shared_with (other: like Current): BOOLEAN
			-- Does string share the text of other?

	substring_index (other: STRING; start: INTEGER): INTEGER
			-- Position of first occurrence of other at or after start;
			-- 0 if none.
		require
			other_nonvoid: other /= void;
			other_notempty: not other.empty;
			start_large_enough: start >= 1;
			start_small_enough: start <= count
		ensure
			correct_place: Result > 0 implies substring (Result, Result + other.count - 1).is_equal (other)

	True_constant: STRING is "true"
			-- Constant string "true"

	infix "@" (i: INTEGER): CHARACTER
			-- Character at position i
			-- Was declared in STRING as synonym of item and @.
		require -- from TABLE
			valid_key: valid_index (k)
	
feature -- Measurement

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

	capacity: INTEGER
			-- Allocated space

	count: INTEGER
			-- Actual number of characters making up the string

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

	index_set: INTEGER_INTERVAL
			-- Range of acceptable indexes
		ensure -- from INDEXABLE
			not_void: Result /= void
		ensure then
			Result.count = count

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

	occurrences (c: CHARACTER): INTEGER
			-- Number of times c appears in the string
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
	
feature -- Comparison

	is_equal (other: like Current): BOOLEAN
			-- Is string made of same character sequence as other
			-- (possibly with a different capacity)?
		require -- COMPARABLE
			precursor: True
		require -- from GENERAL
			other_not_void: other /= void
		ensure then -- from COMPARABLE
			trichotomy: Result = (not (Current < other) and not (other < Current))
		ensure -- from GENERAL
			symmetric: Result implies other.is_equal (Current);
			consistent: standard_is_equal (other) implies Result

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

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

	infix "<" (other: like Current): BOOLEAN
			-- Is string lexicographically lower than other?
		require -- from PART_COMPARABLE
			other_exists: other /= void
		ensure then -- from COMPARABLE
			asymmetric: Result implies not (other < Current)

	infix "<=" (other: like Current): 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 is_equal (other))

	infix ">" (other: like Current): 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)

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

	Changeable_comparison_criterion: BOOLEAN is false

	empty: BOOLEAN
			-- Is structure empty?
			-- (from FINITE)

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

	full: BOOLEAN
			-- Is structure full?
			-- (from BOUNDED)

	is_boolean: BOOLEAN
			-- Is the string representing a boolean?

	is_double: BOOLEAN
			-- Is the string representing a double?

	is_hashable: BOOLEAN
			-- May current object be hashed?
			-- (True if it is not its type's default.)
			-- (from HASHABLE)
		ensure -- from HASHABLE
			ok_if_not_default: Result implies (Current /= default)

	is_integer: BOOLEAN
			-- Is the string representing an integer?

	is_real: BOOLEAN
			-- Is the string representing a real?

	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.)

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

	valid_index (i: INTEGER): BOOLEAN
			-- Is i within the bounds of the string?
		ensure then -- from INDEXABLE
			only_if_in_index_set: Result implies ((i >= index_set.lower) and (i <= index_set.upper))
	
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
		ensure -- from CONTAINER
			object_comparison

	compare_references
			-- Ensure that future search operations will use =
			-- rather than equal for comparing references.
			-- (from CONTAINER)
		require -- from CONTAINER
			changeable_comparison_criterion
		ensure -- from CONTAINER
			reference_comparison: not object_comparison
	
feature -- Element change

	append (s: STRING)
			-- Append a copy of s at end.
		require
			argument_not_void: s /= void
		ensure
			new_count: count = old count + old s.count

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

	append_character (c: CHARACTER)
			-- Append c at end.
			-- Was declared in STRING as synonym of append_character and extend.
		ensure then
			item_inserted: item (count) = c;
			new_count: count = old count + 1

	append_double (d: DOUBLE)
			-- Append the string representation of d at end.

	append_integer (i: INTEGER)
			-- Append the string representation of i at end.

	append_real (r: REAL)
			-- Append the string representation of r at end.

	append_string (s: STRING)
			-- Append a copy of s, if not void, at end.

	copy (other: like Current)
			-- Reinitialize by copying the characters of other.
			-- (This is also used by clone.)
		require -- from GENERAL
			other_not_void: other /= void;
			type_identity: same_type (other)
		ensure -- from GENERAL
			is_equal: is_equal (other)
		ensure then
			new_result_count: count = other.count

	extend (c: CHARACTER)
			-- Append c at end.
			-- Was declared in STRING as synonym of append_character and extend.
		require -- from COLLECTION
			extendible: extendible
		ensure -- from COLLECTION
			item_inserted: has (v)
		ensure then -- from BAG
			one_more_occurrence: occurrences (v) = old (occurrences (v)) + 1
		ensure then
			item_inserted: item (count) = c;
			new_count: count = old count + 1

	fill (other: CONTAINER [CHARACTER])
			-- 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

	fill_blank
			-- Fill with capacity blank characters.
		ensure
			filled: full;
			same_size: (count = capacity) and (capacity = old capacity)

	fill_character (c: CHARACTER)
			-- Fill with capacity characters all equal to c.
		ensure
			filled: full;
			same_size: (count = capacity) and (capacity = old capacity)

	head (n: INTEGER)
			-- Remove all characters except for the first n;
			-- do nothing if n >= count.
		require
			non_negative_argument: n >= 0
		ensure
			new_count: count = n.min (old count)

	insert (s: STRING; i: INTEGER)
			-- Add s to the left of position i in current string.
		require
			string_exists: s /= void;
			index_small_enough: i <= count;
			index_large_enough: i > 0
		ensure
			new_count: count = old count + s.count

	left_adjust
			-- Remove leading whitespace.
		ensure
			new_count: (count /= 0) implies ((item (1) /= ' ') and (item (1) /= '%T') and (item (1) /= '%R') and (item (1) /= '%N'))

	precede (c: CHARACTER)
			-- Add c at front.
		ensure
			new_count: count = old count + 1

	prepend (s: STRING)
			-- Prepend a copy of s at front.
		require
			argument_not_void: s /= void
		ensure
			new_count: count = old count + s.count

	prepend_boolean (b: BOOLEAN)
			-- Prepend the string representation of b at front.

	prepend_character (c: CHARACTER)
			-- Prepend the string representation of c at front.

	prepend_double (d: DOUBLE)
			-- Prepend the string representation of d at front.

	prepend_integer (i: INTEGER)
			-- Prepend the string representation of i at front.

	prepend_real (r: REAL)
			-- Prepend the string representation of r at front.

	prepend_string (s: STRING)
			-- Prepend a copy of s, if not void, at front.

	put (c: CHARACTER; i: INTEGER)
			-- Replace character at position i by c.
		require -- from TABLE
			valid_key: valid_index (k)
		ensure then -- from INDEXABLE
			insertion_done: item (k) = v

	replace_blank
			-- Replace all current characters with blanks.
		ensure
			same_size: (count = old count) and (capacity = old capacity)

	replace_character (c: CHARACTER)
			-- Replace all current characters with characters all equal to c.
		ensure
			same_size: (count = old count) and (capacity = old capacity)

	replace_substring (s: like Current; start_pos, end_pos: INTEGER)
			-- Copy the characters of s to positions
			-- start_pos .. end_pos.
		require
			string_exists: s /= void;
			index_small_enough: end_pos <= count;
			order_respected: start_pos <= end_pos;
			index_large_enough: start_pos > 0
		ensure
			new_count: count = old count + s.count - end_pos + start_pos - 1

	replace_substring_all (original, new: like Current)
			-- Replace every occurence of original with new.
		require
			original_exists: original /= void;
			new_exists: new /= void;
			original_not_empty: not original.empty

	right_adjust
			-- Remove trailing whitespace.
		ensure
			new_count: (count /= 0) implies ((item (count) /= ' ') and (item (count) /= '%T') and (item (count) /= '%R') and (item (count) /= '%N'))

	set (t: like Current; n1, n2: INTEGER)
			-- 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
		ensure
			is_substring: is_equal (t.substring (n1, n2))

	share (other: like Current)
			-- 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
		ensure
			shared_count: other.count = count

	subcopy (other: like Current; start_pos, end_pos, index_pos: INTEGER)
			-- 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)

	tail (n: INTEGER)
			-- Remove all characters except for the last n;
			-- do nothing if n >= count.
		require
			non_negative_argument: n >= 0
		ensure
			new_count: count = n.min (old count)

	infix "+" (s: STRING): STRING
			-- Append a copy of 's' at the end of a copy of Current,
			-- Then return the Result.
		require
			argument_not_void: s /= void
		ensure
			result_exists: Result /= void;
			new_count: Result.count = count + s.count
	
feature -- Removal

	clear_all
			-- Reset all characters.
		ensure
			empty: count = 0;
			same_capacity: capacity = old capacity

	prune (c: CHARACTER)
			-- Remove first occurrence of c, if any.
		require -- from COLLECTION
			prunable: prunable
		require else
			true

	prune_all (c: CHARACTER)
			-- Remove all occurrences of c.
		require -- from COLLECTION
			prunable
		require else
			true
		ensure -- from COLLECTION
			no_more_occurrences: not has (v)
		ensure then
			changed_count: count = (old count) - (old occurrences (c))

	prune_all_leading (c: CHARACTER)
			-- Remove all leading occurrences of c.

	prune_all_trailing (c: CHARACTER)
			-- Remove all trailing occurrences of c.

	remove (i: INTEGER)
			-- Remove i-th character.
		require
			index_small_enough: i <= count;
			index_large_enough: i > 0
		ensure
			new_count: count = old count - 1

	wipe_out
			-- Remove all characters.
		require -- from COLLECTION
			prunable
		ensure -- from COLLECTION
			wiped_out: empty
		ensure then
			empty: count = 0;
			empty_capacity: capacity = 0
	
feature -- Resizing

	adapt_size
			-- Adapt the size to accommodate count characters.

	automatic_grow
			-- Change the capacity to accommodate at least
			-- Growth_percentage more items.
			-- (from RESIZABLE)
		ensure -- from RESIZABLE
			increased_capacity: capacity >= old capacity + old capacity * growth_percentage // 100

	grow (newsize: INTEGER)
			-- Ensure that the capacity is at least newsize.
		require -- RESIZABLE
			precursor: True
		require else
			new_size_non_negative: newsize >= 0
		ensure -- from RESIZABLE
			new_capacity: capacity >= i

	resize (newsize: INTEGER)
			-- Rearrange string so that it can accommodate
			-- at least newsize characters.
			-- Do not lose any previously entered character.
		require
			new_size_non_negative: newsize >= 0
	
feature -- Conversion

	center_justify
			-- Center justify the string using
			-- the capacity as the width

	character_justify (pivot: CHARACTER; position: INTEGER)
			-- 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 /= ' ';
			not_empty: not empty

	left_justify
			-- Left justify the string using
			-- the capacity as the width

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

	mirror
			-- Reverse the order of characters.
			-- "Hello world" -> "dlrow olleH".
		ensure
			same_count: count = old count

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

	right_justify
			-- Right justify the string using
			-- the capacity as the width

	to_boolean: BOOLEAN
			-- Boolean value;
			-- "true" yields True, "false" yields False
			-- (case-insensitive)
		require
			is_boolean: is_boolean

	frozen to_c: ANY
			-- A reference to a C form of current string.
			-- Useful only for interfacing with C software.

	to_double: DOUBLE
			-- "Double" value;
			-- for example, when applied to "123.0", will yield 123.0 (double)
		require
			is_double: is_double

	to_integer: INTEGER
			-- Integer value;
			-- for example, when applied to "123", will yield 123
		require
			is_integer: is_integer

	to_lower
			-- Convert to lower case.

	to_real: REAL
			-- Real value;
			-- for example, when applied to "123.0", will yield 123.0
		require
			is_real: is_real

	to_upper
			-- Convert to upper case.
	
feature -- Duplication

	multiply (n: INTEGER)
			-- Duplicate a string within itself
			-- ("hello").multiply(3) => "hellohellohello"
		require
			meaningful_multiplier: n >= 1

	substring (n1, n2: INTEGER): like Current
			-- Copy of substring containing all characters at indices
			-- between n1 and n2
		ensure
			new_result_count: Result.count = n2 - n1 + 1 or Result.count = 0
	
feature -- Output

	out: like Current
			-- Printable representation
	
invariant

		-- from GENERAL
	reflexive_equality: standard_is_equal (Current);
	reflexive_conformance: conforms_to (Current);
	extendible: extendible;
	compare_character: object_comparison = false;
	index_set_has_same_count: index_set.count = count;
		-- from INDEXABLE
	index_set_not_void: index_set /= void;
		-- 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: empty = (count = 0);
	non_negative_count: count >= 0;
		-- from COMPARABLE
	irreflexive_comparison: not (Current < Current);

end -- class STRING