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