    indexing
    	description: "[
    		Contiguous integer interval that calls an action sequence
    		when it changes.
    	]"
    	legal: "See notice at end of class."
    	status: "See notice at end of class."
    	keywords: "event, action, linked, list"
    	date: "$Date: 2006-01-22 18:25:44 -0800 (Sun, 22 Jan 2006) $"
    	revision: "$Revision: 56675 $"

    class interface
    	ACTIVE_INTEGER_INTERVAL

    create
    	make (min_index, max_index: INTEGER_32)
    			-- Set up interval to have bounds `min_index' and
    			-- `max_index' (empty if `min_index' > `max_index')
    			-- (from INTEGER_INTERVAL)
    		ensure -- from INTEGER_INTERVAL
    			lower_defined: lower_defined
    			upper_defined: upper_defined
    			set_if_non_empty: (min_index <= max_index) implies ((lower = min_index) and (upper = max_index))
    			empty_if_not_in_order: (min_index > max_index) implies is_empty

    feature -- Initialization

    	adapt (other: INTEGER_INTERVAL)
    			-- Reset to be the same interval as `other'.
    		require -- from INTEGER_INTERVAL
    			other_not_void: other /= Void
    		ensure -- from INTEGER_INTERVAL
    			same_lower: lower = other.lower
    			same_upper: upper = other.upper
    			same_lower_defined: lower_defined = other.lower_defined
    			same_upper_defined: upper_defined = other.upper_defined

    feature -- Access

    	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)

    	has (v: INTEGER_32): BOOLEAN
    			-- Does `v' appear in interval?
    			-- Was declared in INTEGER_INTERVAL as synonym of valid_index.
    			-- (from INTEGER_INTERVAL)
    		require -- from  CONTAINER
    			True
    		ensure -- from CONTAINER
    			not_found_in_empty: Result implies not is_empty
    		ensure then -- from INTEGER_INTERVAL
    			iff_within_bounds: Result = ((upper_defined implies v <= upper) and (lower_defined implies v >= lower))

    	item alias "[]" (i: INTEGER_32): INTEGER_32
    			-- Entry at index `i', if in index interval
    			-- Was declared in INTEGER_INTERVAL as synonym of infix "@".
    			-- (from INTEGER_INTERVAL)
    		require -- from TABLE
    			valid_key: valid_index (i)

    	lower: INTEGER_32
    			-- Smallest value in interval
    			-- (from INTEGER_INTERVAL)
    		require -- from INTEGER_INTERVAL
    			lower_defined: lower_defined

    	lower_defined: BOOLEAN
    			-- Is there a lower bound?
    			-- (from INTEGER_INTERVAL)

    	upper: INTEGER_32
    			-- Largest value in interval
    			-- (from INTEGER_INTERVAL)
    		require -- from INTEGER_INTERVAL
    			upper_defined: upper_defined

    	upper_defined: BOOLEAN
    			-- Is there an upper bound?
    			-- (from INTEGER_INTERVAL)

    	valid_index (v: INTEGER_32): BOOLEAN
    			-- Does `v' appear in interval?
    			-- Was declared in INTEGER_INTERVAL as synonym of has.
    			-- (from INTEGER_INTERVAL)
    		require -- from  TABLE
    			True
    		ensure then -- from INDEXABLE
    			only_if_in_index_set: Result implies ((v >= index_set.lower) and (v <= index_set.upper))
    		ensure then -- from INTEGER_INTERVAL
    			iff_within_bounds: Result = ((upper_defined implies v <= upper) and (lower_defined implies v >= lower))

    	infix "@" (i: INTEGER_32): INTEGER_32
    			-- Entry at index `i', if in index interval
    			-- Was declared in INTEGER_INTERVAL as synonym of item.
    			-- (from INTEGER_INTERVAL)
    		require -- from TABLE
    			valid_key: valid_index (i)

    feature -- Measurement

    	additional_space: INTEGER_32
    			-- Proposed number of additional items
    			-- (from RESIZABLE)
    		ensure -- from RESIZABLE
    			at_least_one: Result >= 1

    	capacity: INTEGER_32
    			-- Maximum number of items in interval
    			-- (here the same thing as count)
    			-- (from INTEGER_INTERVAL)

    	count: INTEGER_32
    			-- Number of items in interval
    			-- (from INTEGER_INTERVAL)
    		require -- from  SET
    			True
    		require -- from  FINITE
    			True
    		ensure then -- from INTEGER_INTERVAL
    			definition: Result = upper - lower + 1

    	growth_percentage: INTEGER_32 is 50
    			-- Percentage by which structure will grow automatically
    			-- (from RESIZABLE)

    	index_set: INTEGER_INTERVAL
    			-- Range of acceptable indexes
    			-- (here: the interval itself)
    			-- (from INTEGER_INTERVAL)
    		require -- from  INDEXABLE
    			True
    		ensure -- from INDEXABLE
    			not_void: Result /= Void
    		ensure then -- from INTEGER_INTERVAL
    			index_set_is_range: equal (Result, Current)

    	minimal_increase: INTEGER_32 is 5
    			-- Minimal number of additional items
    			-- (from RESIZABLE)

    	occurrences (v: INTEGER_32): INTEGER_32
    			-- Number of times `v' appears in structure
    			-- (from INTEGER_INTERVAL)
    		require -- from  BAG
    			True
    		ensure -- from BAG
    			non_negative_occurrences: Result >= 0
    		ensure then -- from INTEGER_INTERVAL
    			one_iff_in_bounds: Result = 1 implies has (v)
    			zero_otherwise: Result /= 1 implies Result = 0

    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 array made of the same items as `other'?
    			-- (from INTEGER_INTERVAL)
    		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 INTEGER_INTERVAL
    			iff_same_bounds: Result = ((lower_defined implies (other.lower_defined and lower = other.lower)) and (upper_defined implies (other.upper_defined and upper = other.upper)))

    	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)

    feature -- Status report

    	all_cleared: BOOLEAN
    			-- Are all items set to default values?
    			-- (from INTEGER_INTERVAL)
    		ensure then -- from INTEGER_INTERVAL
    			iff_at_zero: Result = ((lower = 0) and (upper = 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

    	extendible: BOOLEAN
    			-- May new items be added?
    			-- Answer: yes
    			-- (from INTEGER_INTERVAL)

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

    	is_empty: BOOLEAN
    			-- Is structure empty?
    			-- (from FINITE)
    		require -- from  CONTAINER
    			True

    	is_inserted (v: INTEGER_32): BOOLEAN
    			-- Has `v' been inserted by the most recent insertion?
    			-- (By default, the value returned is equivalent to calling
    			-- `has (v)'. However, descendants might be able to provide more
    			-- efficient implementations.)
    			-- (from COLLECTION)

    	object_comparison: BOOLEAN
    			-- Must search operations use equal rather than `='
    			-- for comparing references? (Default: no, use `='.)
    			-- (from CONTAINER)

    	prunable: BOOLEAN
    			-- May individual items be removed?
    			-- Answer: no
    			-- (from INTEGER_INTERVAL)

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

    	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))

    feature -- Status setting

    	compare_objects
    			-- Ensure that future search operations will use equal
    			-- rather than `=' for comparing references.
    			-- (from CONTAINER)
    		require -- from CONTAINER
    			changeable_comparison_criterion: changeable_comparison_criterion
    		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: changeable_comparison_criterion
    		ensure -- from CONTAINER
    			reference_comparison: not object_comparison

    feature -- Element change

    	extend (v: INTEGER_32)
    			-- Make sure that interval goes all the way
    			-- to `v' (up or down).
    		require -- from COLLECTION
    			extendible: extendible
    		ensure -- from COLLECTION
    			item_inserted: is_inserted (v)
    		ensure then -- from SET
    			in_set_already: old has (v) implies (count = old count)
    			added_to_set: not old has (v) implies (count = old count + 1)
    		ensure then -- from BAG
    			one_more_occurrence: occurrences (v) = old (occurrences (v)) + 1
    		ensure then -- from INTEGER_INTERVAL
    			extended_down: lower = (old lower).min (v)
    			extended_up: upper = (old upper).max (v)

    	fill (other: CONTAINER [INTEGER_32])
    			-- Fill with as many items of `other' as possible.
    			-- The representations of `other' and current structure
    			-- need not be the same.
    			-- (from COLLECTION)
    		require -- from COLLECTION
    			other_not_void: other /= Void
    			extendible: extendible

    	put (v: INTEGER_32)
    			-- Make sure that interval goes all the way
    			-- to `v' (up or down).
    		require -- from COLLECTION
    			extendible: extendible
    		require -- from  INTEGER_INTERVAL
    			True
    		ensure -- from COLLECTION
    			item_inserted: is_inserted (v)
    		ensure then -- from SET
    			in_set_already: old has (v) implies (count = old count)
    			added_to_set: not old has (v) implies (count = old count + 1)
    		ensure then -- from INTEGER_INTERVAL
    			extended_down: lower = (old lower).min (v)
    			extended_up: upper = (old upper).max (v)

    feature -- Removal

    	changeable_comparison_criterion: BOOLEAN
    			-- May object_comparison be changed?
    			-- (Answer: only if set empty; otherwise insertions might
    			-- introduce duplicates, destroying the set property.)
    			-- (from SET)
    		require -- from  CONTAINER
    			True
    		ensure then -- from SET
    			only_on_empty: Result = is_empty

    	prune_all (v: INTEGER_32)
    			-- Remove all occurrences of `v'.
    			-- (Reference or object equality,
    			-- based on object_comparison.)
    			-- (from COLLECTION)
    		require -- from COLLECTION
    			prunable: prunable
    		ensure -- from COLLECTION
    			no_more_occurrences: not has (v)

    	wipe_out
    			-- Remove all items.
    			-- (from INTEGER_INTERVAL)
    		require -- from COLLECTION
    			prunable: prunable
    		ensure -- from COLLECTION
    			wiped_out: is_empty

    feature -- Resizing

    	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 (i: INTEGER_32)
    			-- Ensure that capacity is at least `i'.
    			-- (from INTEGER_INTERVAL)
    		require -- from  RESIZABLE
    			True
    		ensure -- from RESIZABLE
    			new_capacity: capacity >= i
    		ensure then -- from INTEGER_INTERVAL
    			no_loss_from_bottom: lower <= old lower
    			no_loss_from_top: upper >= old upper

    	resize (min_index, max_index: INTEGER_32)
    			-- Rearrange interval to go from at most
    			-- `min_index' to at least `max_index',
    			-- encompassing previous bounds.

    	resize_exactly (min_index, max_index: INTEGER_32)
    			-- Rearrange interval to go from
    			-- `min_index' to `max_index'.

    feature -- Conversion

    	as_array: ARRAY [INTEGER_32]
    			-- Plain array containing interval's items
    			-- (from INTEGER_INTERVAL)
    		require -- from INTEGER_INTERVAL
    			finite: upper_defined and lower_defined
    		ensure -- from INTEGER_INTERVAL
    			same_lower: Result.lower = lower
    			same_upper: Result.upper = upper

    	linear_representation: LINEAR [INTEGER_32]
    			-- Representation as a linear structure
    			-- (from INTEGER_INTERVAL)

    feature -- Duplication

    	copy (other: like Current)
    			-- Reset to be the same interval as `other'.
    		require -- from ANY
    			other_not_void: other /= Void
    			type_identity: same_type (other)
    		ensure -- from ANY
    			is_equal: is_equal (other)
    		ensure then -- from INTEGER_INTERVAL
    			same_lower: lower = other.lower
    			same_upper: upper = other.upper
    			same_lower_defined: lower_defined = other.lower_defined
    			same_upper_defined: upper_defined = other.upper_defined

    	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)

    	subinterval (start_pos, end_pos: INTEGER_32): like Current
    			-- Interval made of items of current array within
    			-- bounds `start_pos' and `end_pos'.
    			-- (from INTEGER_INTERVAL)

    	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 -- Event handling

    	change_actions: ACTION_SEQUENCE [TUPLE]
    			-- Actions performed when interval changes.
    		ensure
    			not_void: Result /= Void

    feature -- Iteration

    	do_all (action: PROCEDURE [ANY, TUPLE [INTEGER_32]])
    			-- Apply `action' to every item of current interval.
    			-- (from INTEGER_INTERVAL)
    		require -- from INTEGER_INTERVAL
    			action_exists: action /= Void
    			finite: upper_defined and lower_defined

    	exists (condition: FUNCTION [ANY, TUPLE [INTEGER_32], BOOLEAN]): BOOLEAN
    			-- Does at least one of  interval's values
    			-- satisfy `condition'?
    			-- (from INTEGER_INTERVAL)
    		require -- from INTEGER_INTERVAL
    			finite: upper_defined and lower_defined
    			condition_not_void: condition /= Void
    		ensure -- from INTEGER_INTERVAL
    			consistent_with_count: Result = (hold_count (condition) > 0)

    	exists1 (condition: FUNCTION [ANY, TUPLE [INTEGER_32], BOOLEAN]): BOOLEAN
    			-- Does exactly one of  interval's values
    			-- satisfy `condition'?
    			-- (from INTEGER_INTERVAL)
    		require -- from INTEGER_INTERVAL
    			finite: upper_defined and lower_defined
    			condition_not_void: condition /= Void
    		ensure -- from INTEGER_INTERVAL
    			consistent_with_count: Result = (hold_count (condition) = 1)

    	for_all (condition: FUNCTION [ANY, TUPLE [INTEGER_32], BOOLEAN]): BOOLEAN
    			-- Do all interval's values satisfy `condition'?
    			-- (from INTEGER_INTERVAL)
    		require -- from INTEGER_INTERVAL
    			finite: upper_defined and lower_defined
    			condition_not_void: condition /= Void
    		ensure -- from INTEGER_INTERVAL
    			consistent_with_count: Result = (hold_count (condition) = count)

    	hold_count (condition: FUNCTION [ANY, TUPLE [INTEGER_32], BOOLEAN]): INTEGER_32
    			-- Number of  interval's values that
    			-- satisfy `condition'
    			-- (from INTEGER_INTERVAL)
    		require -- from INTEGER_INTERVAL
    			finite: upper_defined and lower_defined
    			condition_not_void: condition /= Void
    		ensure -- from INTEGER_INTERVAL
    			non_negative: Result >= 0

    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)

    invariant
    		-- from INTEGER_INTERVAL
    	count_definition: upper_defined and lower_defined implies count = upper - lower + 1
    	index_set_is_range: equal (index_set, Current)
    	not_infinite: upper_defined and lower_defined

    		-- from RESIZABLE
    	increase_by_at_least_one: minimal_increase >= 1

    		-- from BOUNDED
    	valid_count: count <= capacity
    	full_definition: full = (count = capacity)

    		-- from FINITE
    	empty_definition: is_empty = (count = 0)
    	non_negative_count: count >= 0

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

    		-- from INDEXABLE
    	index_set_not_void: index_set /= Void

    indexing
    	library: "EiffelBase: Library of reusable components for Eiffel."
    	copyright: "Copyright (c) 1984-2006, Eiffel Software and others"
    	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
    	source: "[
    		Eiffel Software
    		356 Storke Road, 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 ACTIVE_INTEGER_INTERVAL