    indexing
    	description: "Intervals between absolute values"
    	legal: "See notice at end of class."
    	status: "See notice at end of class."
    	date: "$Date: 2006-01-22 18:25:44 -0800 (Sun, 22 Jan 2006) $"
    	revision: "$Revision: 56675 $"

    class interface
    	INTERVAL [G -> ABSOLUTE]

    create
    	make (s, e: G)
    			-- Sets start_bound and end_bound to `s' and `e' respectively.
    		require
    			start_exists: s /= Void
    			end_exists: e /= Void
    			start_before_end: s <= e
    		ensure
    			start_bound_set: start_bound /= Void and then deep_equal (start_bound, s)
    			end_bound_set: end_bound /= Void and then deep_equal (end_bound, e)

    feature -- Initialization

    	make (s, e: G)
    			-- Sets start_bound and end_bound to `s' and `e' respectively.
    		require
    			start_exists: s /= Void
    			end_exists: e /= Void
    			start_before_end: s <= e
    		ensure
    			start_bound_set: start_bound /= Void and then deep_equal (start_bound, s)
    			end_bound_set: end_bound /= Void and then deep_equal (end_bound, e)

    feature -- Access

    	end_bound: G
    			-- End bound of the current interval

    	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)

    	start_bound: G
    			-- Start bound of the current interval

    feature -- Measurement

    	duration: DURATION
    			-- Length of the interval

    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))

    	includes (other: like Current): BOOLEAN
    			-- Does current interval include `other'?
    		require -- from PART_COMPARABLE
    			other_exists: other /= Void

    	intersects (other: like Current): BOOLEAN
    			-- Does current interval intersect `other'?
    		require
    			other_exists: other /= Void

    	is_equal (other: like Current): BOOLEAN
    			-- Is current interval equal to `other'?
    		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

    	is_included_by (other: like Current): BOOLEAN
    			-- Is current interval included by `other'?
    		require -- from PART_COMPARABLE
    			other_exists: other /= Void

    	is_met_by (other: like Current): BOOLEAN
    			-- Is current interval met by `other'?
    		require
    			other_exists: other /= Void
    		ensure
    			symmetry: Result = other.meets (Current)

    	is_overlapped_by (other: like Current): BOOLEAN
    			-- Is current interval overlapped by `other'?
    		require
    			other_exists: other /= Void
    		ensure
    			symmetry: Result = other.overlaps (Current)

    	is_strict_included_by (other: like Current): BOOLEAN
    			-- Is current interval strictly included by `other'?
    		require -- from PART_COMPARABLE
    			other_exists: other /= Void

    	meets (other: like Current): BOOLEAN
    			-- Does current interval meet `other'?
    		require
    			other_exists: other /= Void
    		ensure
    			symmetry: Result = other.is_met_by (Current)
    			result_definition: Result = (Current <= other and intersects (other))

    	overlaps (other: like Current): BOOLEAN
    			-- Does current interval overlap `other'?
    		require
    			other_exists: other /= Void
    		ensure
    			result_defition: Result = (strict_before (other.end_bound) and has (other.start_bound))
    			symmetry: Result = other.is_overlapped_by (Current)

    	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)

    	strict_includes (other: like Current): BOOLEAN
    			-- Does current interval strictly include `other'?
    		require -- from PART_COMPARABLE
    			other_exists: other /= Void

    	infix "<" (other: like Current): BOOLEAN
    			-- Is current interval strictly before `other'?
    		require -- from PART_COMPARABLE
    			other_exists: other /= Void

    	infix "<=" (other: like Current): BOOLEAN
    			-- Is current interval before `other'?
    		require -- from PART_COMPARABLE
    			other_exists: other /= Void

    	infix ">" (other: like Current): BOOLEAN
    			-- Is current interval after `other'?
    		require -- from PART_COMPARABLE
    			other_exists: other /= Void

    	infix ">=" (other: like Current): BOOLEAN
    			-- Is current interval after `other'?
    		require -- from PART_COMPARABLE
    			other_exists: other /= Void

    feature -- Status report

    	after (v: G): BOOLEAN
    			-- Is the current interval after `v'?
    		require
    			exists: v /= Void
    		ensure
    			result_definition: Result = (start_bound >= v)

    	before (v: G): BOOLEAN
    			-- Is the current interval before `v'?
    		require
    			exists: v /= Void
    		ensure
    			result_definition: Result = (end_bound <= v)

    	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

    	empty: BOOLEAN
    			-- Is current interval empty?
    		ensure
    			result_definition: Result = duration.is_equal (duration.zero)

    	has (v: G): BOOLEAN
    			-- Does current interval have `v' between its bounds?
    		require
    			exists: v /= Void
    		ensure
    			result_definition: Result xor not ((start_bound <= v) and then (end_bound >= v))

    	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))

    	strict_after (v: G): BOOLEAN
    			-- Is the current interval strictly after `v'?
    		require
    			exists: v /= Void
    		ensure
    			result_definition: Result = (start_bound > v)

    	strict_before (v: G): BOOLEAN
    			-- Is the current interval strictly before `v'?
    		require
    			exists: v /= Void
    		ensure
    			result_definition: Result xor (not (end_bound < v))

    feature -- Element change

    	set_end_bound (e: G)
    			-- Set end_bound to `e'.
    		require
    			end_bound_exists: e /= Void
    			end_after_start_bound: e >= start_bound
    		ensure
    			end_bound_set: equal (end_bound, e)

    	set_start_bound (s: G)
    			-- Set start_bound to `s'.
    		require
    			start_bound_exists: s /= Void
    			start_before_end_bound: s <= end_bound
    		ensure
    			start_bound_set: equal (start_bound, s)

    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)

    	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)

    	gather (other: like Current): like Current
    			-- Union of `other' and current interval if `other' meets
    			-- current interval
    		require
    			other_exist: other /= Void
    			meeting_interval: meets (other)
    		ensure
    			result_exist: Result /= Void
    			result_same_as_union: Result.is_equal (union (other))

    	intersection (other: like Current): like Current
    			-- Intersection with `other'
    		require
    			other_exists: other /= Void
    		ensure
    			intersects_validity: intersects (other) implies Result /= Void
    			result_is_included_by_current: intersects (other) implies includes (Result)
    			result_is_included_by_other: intersects (other) implies other.includes (Result)

    	union (other: like Current): like Current
    			-- Union with `other'
    		require
    			other_exists: other /= Void
    			intersects: intersects (other)
    		ensure
    			result_exists: Result /= Void
    			result_includes_current: Result.includes (Current)
    			result_includes_other: Result.includes (other)

    feature -- Output

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

    	out: STRING_8
    			-- Printable representation of the current interval

    	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
    	start_bound_exists: start_bound /= Void
    	end_bound_exists: end_bound /= Void
    	start_bound_before_end_bound: start_bound <= end_bound
    	current_intersection: intersection (Current).is_equal (Current)
    	current_union: union (Current).is_equal (Current)
    	has_bounds: has (start_bound) and has (end_bound)
    	between_bound: after (start_bound) and before (end_bound)

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

    indexing
    	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 INTERVAL