    indexing
    	description: "Common ancestors to all STRING classes."
    	date: "$Date: 2006-09-20 15:19:17 -0700 (Wed, 20 Sep 2006) $"
    	revision: "$Revision: 63744 $"

    deferred class interface
    	STRING_GENERAL

    convert
    	as_string_32: {STRING_32},
    	to_cil: {SYSTEM_STRING}

    feature -- Access

    	code (i: INTEGER_32): NATURAL_32
    			-- Code at position `i'
    		require
    			valid_index: valid_index (i)

    	generating_type: STRING_8
    			-- Name of current object's generating type
    			-- (type of which it is a direct instance)
    			-- (from ANY)

    	generator: STRING_8
    			-- Name of current object's generating class
    			-- (base class of the type of which it is a direct instance)
    			-- (from ANY)

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

    	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.
    		require
    			start_large_enough: start_index >= 1
    			start_small_enough: start_index <= count + 1
    		ensure
    			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)

    feature -- Comparison

    	frozen deep_equal (some: ANY; other: like arg #1): BOOLEAN
    			-- Are `some' and `other' either both void
    			-- or attached to isomorphic object structures?
    			-- (from ANY)
    		ensure -- from ANY
    			shallow_implies_deep: standard_equal (some, other) implies Result
    			both_or_none_void: (some = Void) implies (Result = (other = Void))
    			same_type: (Result and (some /= Void)) implies some.same_type (other)
    			symmetric: Result implies deep_equal (other, some)

    	frozen equal (some: ANY; other: like arg #1): BOOLEAN
    			-- Are `some' and `other' either both void or attached
    			-- to objects considered equal?
    			-- (from ANY)
    		ensure -- from ANY
    			definition: Result = (some = Void and other = Void) or else ((some /= Void and other /= Void) and then some.is_equal (other))

    	is_equal (other: like Current): BOOLEAN
    			-- Is `other' attached to an object of the same type
    			-- as current object and identical to it?
    			-- (from COMPARABLE)
    		require -- from ANY
    			other_not_void: other /= Void
    		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))

    	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

    	frozen standard_equal (some: ANY; other: like arg #1): BOOLEAN
    			-- Are `some' and `other' 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
    			definition: Result = (some = Void and other = Void) or else ((some /= Void and other /= Void) and then some.standard_is_equal (other))

    	frozen standard_is_equal (other: like Current): 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)

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

    	infix "<" (other: like Current): BOOLEAN
    			-- Is current object less than `other'?
    			-- (from COMPARABLE)
    		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

    	capacity: INTEGER_32
    			-- Number of characters allocated in Current
    		ensure
    			capacity_non_negative: Result >= 0

    	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

    	count: INTEGER_32
    			-- Number of characters in Current
    		ensure
    			count_non_negative: Result >= 0

    	has_code (c: like code): BOOLEAN
    			-- Does string include `c'?
    		ensure then
    			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_empty: BOOLEAN
    			-- Is structure empty?

    	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_string_32: BOOLEAN
    			-- Is `Current' a STRING_32?

    	is_string_8: BOOLEAN
    			-- Is `Current' a STRING_8?

    	is_valid_as_string_8: BOOLEAN
    			-- Is `Current' convertible to STRING_8 without information loss?

    	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))

    	valid_code (v: like code): BOOLEAN
    			-- Is `v' a valid code for Current?

    	valid_index (i: INTEGER_32): BOOLEAN
    			-- Is `i' within the bounds of the string?

    feature -- Element change

    	append (s: STRING_GENERAL)
    			-- Append a copy of `s' at end.
    		require
    			argument_not_void: s /= Void
    			compatible_strings: is_string_8 implies s.is_valid_as_string_8
    		ensure
    			new_count: count = old count + old s.count
    			appended: elks_checking implies to_string_32.is_equal (old to_string_32.twin + old s.to_string_32.twin)

    	append_code (c: like code)
    			-- Append `c' at end.
    		require
    			valid_code: valid_code (c)
    		ensure then
    			item_inserted: code (count) = c
    			new_count: count = old count + 1
    			stable_before: elks_checking implies substring (1, count - 1).is_equal (old twin)

    feature -- Removal

    	remove (i: INTEGER_32)
    			-- Remove `i'-th character.
    		require
    			valid_index: valid_index (i)
    		ensure
    			new_count: count = old count - 1
    			removed: elks_checking implies to_string_32.is_equal (old substring (1, i - 1).to_string_32 + old substring (i + 1, count).to_string_32)

    feature -- Resizing

    	resize (newsize: INTEGER_32)
    			-- 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

    	as_string_32: STRING_32
    			-- Convert `Current' as a STRING_32.
    			-- Was declared in STRING_GENERAL as synonym of to_string_32.
    		ensure
    			as_string_32_not_void: Result /= Void
    			identity: (is_string_32 and Result = Current) or (not is_string_32 and Result /= Current)

    	as_string_8: STRING_8
    			-- Convert `Current' as a STRING_8. If a code of `Current' is
    			-- node a valid code for a STRING_8 it is replaced with the null
    			-- character.
    		ensure
    			as_string_8_not_void: Result /= Void
    			identity: (is_string_8 and Result = Current) or (not is_string_8 and Result /= Current)

    	frozen to_cil: SYSTEM_STRING
    			-- Create an instance of SYSTEM_STRING using characters
    			-- of Current between indices `1' and count.
    		require
    			is_dotnet: {PLATFORM}.is_dotnet
    		ensure
    			to_cil_not_void: Result /= Void

    	to_string_32: STRING_32
    			-- Convert `Current' as a STRING_32.
    			-- Was declared in STRING_GENERAL as synonym of as_string_32.
    		ensure
    			as_string_32_not_void: Result /= Void
    			identity: (is_string_32 and Result = Current) or (not is_string_32 and Result /= Current)

    	to_string_8: STRING_8
    			-- Convert `Current' as a STRING_8.
    		require
    			is_valid_as_string_8: is_valid_as_string_8
    		ensure
    			as_string_8_not_void: Result /= Void
    			identity: (is_string_8 and Result = Current) or (not is_string_8 and Result /= Current)

    feature -- Duplication

    	copy (other: like Current)
    			-- Update current object using fields of object attached
    			-- to `other', so as to yield equal objects.
    			-- (from ANY)
    		require -- from ANY
    			other_not_void: other /= Void
    			type_identity: same_type (other)
    		ensure -- from ANY
    			is_equal: is_equal (other)

    	frozen deep_copy (other: like Current)
    			-- 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: like Current
    			-- New object structure recursively duplicated from Current.
    			-- (from ANY)
    		ensure -- from ANY
    			deep_equal: deep_equal (Current, Result)

    	frozen standard_copy (other: like Current)
    			-- 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: like Current
    			-- 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)

    	substring (start_index, end_index: INTEGER_32): like Current
    			-- Copy of substring containing all characters at indices
    			-- between `start_index' and `end_index'
    		ensure
    			substring_not_void: Result /= Void
    			substring_count: Result.count = end_index - start_index + 1 or Result.count = 0
    			first_item: Result.count > 0 implies Result.code (1) = code (start_index)
    			recurse: Result.count > 0 implies Result.substring (2, Result.count).is_equal (substring (start_index + 1, end_index))

    	frozen twin: like Current
    			-- New object equal to `Current'
    			-- twin calls copy; to change copying/twining semantics, redefine copy.
    			-- (from ANY)
    		ensure -- from ANY
    			twin_not_void: Result /= Void
    			is_equal: Result.is_equal (Current)

    feature -- Basic operations

    	frozen default: like Current
    			-- 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)

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

    	frozen do_nothing
    			-- Execute a null action.
    			-- (from ANY)

    feature -- Output

    	io: STD_FILES
    			-- Handle to standard file setup
    			-- (from ANY)

    	out: STRING_8
    			-- New string containing terse printable representation
    			-- of current object
    			-- Was declared in ANY as synonym of tagged_out.
    			-- (from ANY)

    	print (some: ANY)
    			-- Write terse external representation of `some'
    			-- on standard output.
    			-- (from ANY)

    	frozen tagged_out: STRING_8
    			-- New string containing terse printable representation
    			-- of current object
    			-- Was declared in ANY as synonym of out.
    			-- (from ANY)

    feature -- Platform

    	operating_environment: OPERATING_ENVIRONMENT
    			-- Objects available from the operating system
    			-- (from ANY)

    feature -- Settings

    	put_code (v: like code; i: INTEGER_32)
    			-- Put code `v' at position `i'.
    		require
    			valid_code: valid_code (v)
    			valid_index: valid_index (i)
    		ensure
    			inserted: code (i) = v
    			stable_count: count = old count
    			stable_before_i: elks_checking implies substring (1, i - 1).is_equal (old substring (1, i - 1))
    			stable_after_i: elks_checking implies substring (i + 1, count).is_equal (old substring (i + 1, count))

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

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

    end -- class STRING_GENERAL