note
	description: "Duration of dates and times"
	legal: "See notice at end of class."
	status: "See notice at end of class."
	date: "$Date: 2017-03-29 12:26:46 +0000 (Wed, 29 Mar 2017) $"
	revision: "$Revision: 100065 $"
	access: date, time

class 
	DATE_TIME_DURATION

create 
	make,
	make_definite,
	make_fine,
	make_by_date_time,
	make_by_date

feature -- Initialization

	make (y, mo, d, h, mi, s: INTEGER_32)
			-- Set year, month, day to y, mo, d.
			-- Set hour, minute, second to h, mi, s.
		do
			create date.make (y, mo, d)
			create time.make (h, mi, s)
		ensure
			date_exists: date /= Void
			time_exists: time /= Void
			year_set: year = y
			month_set: month = mo
			day_set: day = d
			hour_set: hour = h
			minute_set: minute = mi
			second_set: second = s
		end

	make_by_date (d: DATE_DURATION)
			-- Set date to d and time to zero.
		require
			d_exists: d /= Void
		do
			date := d
			create time.make (0, 0, 0)
		ensure
			date_set: date = d
			time_exists: time /= Void
			time_set: time.is_equal (time.zero)
		end

	make_by_date_time (d: DATE_DURATION; t: TIME_DURATION)
			-- Set date to d and time to t.
		require
			date_exists: d /= Void
			time_exists: t /= Void
		do
			date := d
			time := t
		ensure
			date_set: date = d
			time_set: time = t
		end

	make_definite (d, h, m, s: INTEGER_32)
			-- Set day to d.
			-- Set hour, minute, second to h, m, s.
		do
			create date.make_by_days (d)
			create time.make (h, m, s)
		ensure
			date_exists: date /= Void
			time_exists: time /= Void
			definite_result: definite
			day_set: day = d
			hour_set: hour = h
			minute_set: minute = m
			second_set: second = s
		end

	make_fine (y, mo, d, h, mi: INTEGER_32; s: REAL_64)
			-- set year, month, day to y, mo, d.
			-- set hour, minute, second to h, mi, s.
		do
			create date.make (y, mo, d)
			create time.make_fine (h, mi, s)
		ensure
			date_exists: date /= Void
			time_exists: time /= Void
			year_set: year = y
			month_set: month = mo
			day_set: day = d
			hour_set: hour = h
			minute_set: minute = mi
			fine_second_set: fine_second = s
		end
	
feature {NONE} -- Initialization

	default_create
			-- Process instances of classes with no creation clause.
			-- (Default: do nothing.)
			-- (from ANY)
		do
		end
	
feature -- Access

	date: DATE_DURATION
			-- Date part of the current duration

	date_default_format_string: STRING_8
			-- Default output format for dates
			-- (from DATE_CONSTANTS)
		do
			Result := Date_time_tools.Date_default_format_string
		end

	Date_time_tools: DATE_TIME_TOOLS
			-- Tools for outputting dates and times in different formats
			-- (from TIME_UTILITY)
		once
			create Result
		end

	day: INTEGER_32
			-- Day of the current object
			-- (from DATE_TIME_MEASUREMENT)
		do
			Result := date.day
		ensure -- from DATE_TIME_MEASUREMENT
			same_day: Result = date.day
		end

	days_in_i_th_month (i, y: INTEGER_32): INTEGER_32
			-- Number of days in the i th month at year y
			-- (from DATE_CONSTANTS)
		require -- from DATE_CONSTANTS
			i_large_enough: i >= 1
			i_small_enough: i <= Months_in_year
		do
			Result := Days_in_months @ i
			if i = 2 and then is_leap_year (y) then
				Result := Result + 1
			end
		end

	Days_in_leap_year: INTEGER_32 = 366
			-- Number of days in a leap year
			-- (from DATE_CONSTANTS)

	Days_in_non_leap_year: INTEGER_32 = 365
			-- Number of days in a non-leap year
			-- (from DATE_CONSTANTS)

	Days_in_week: INTEGER_32 = 7
			-- Number of days in a week
			-- (from DATE_CONSTANTS)

	days_text: ARRAY [STRING_8]
			-- Short text representation of days
			-- (from DATE_CONSTANTS)
		do
			Result := Date_time_tools.Days_text
		end

	default_format_string: STRING_8
			-- Default output format string
			-- (from TIME_UTILITY)
		do
			Result := Date_time_tools.Default_format_string
		end

	fine_second: REAL_64
			-- Representation of second with decimals
			-- (from DATE_TIME_MEASUREMENT)
		do
			Result := time.fine_second
		ensure -- from DATE_TIME_MEASUREMENT
			same_fine_second: Result = time.fine_second
		end

	fine_seconds_count: REAL_64
			-- Total number of seconds of current duration
		require
			has_origin: has_origin_date_time
		do
			Result := (date.days_count.to_double * Seconds_in_day.to_double) + time.fine_seconds_count
		end

	generating_type: TYPE [detachable DATE_TIME_DURATION]
			-- Type of current object
			-- (type of which it is a direct instance)
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			generating_type_not_void: Result /= Void
		end

	generator: STRING_8
			-- Name of current object's generating class
			-- (base class of the type of which it is a direct instance)
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			generator_not_void: Result /= Void
			generator_not_empty: not Result.is_empty
		end

	hour: INTEGER_32
			-- Hour of the current object
			-- (from DATE_TIME_MEASUREMENT)
		do
			Result := time.hour
		ensure -- from DATE_TIME_MEASUREMENT
			same_hour: Result = time.hour
		end

	Hours_in_day: INTEGER_32 = 24
			-- Number of hours in a day
			-- (from TIME_CONSTANTS)

	long_days_text: ARRAY [STRING_8]
			-- Long text representation of days
			-- (from DATE_CONSTANTS)
		do
			Result := Date_time_tools.Long_days_text
		end

	long_months_text: ARRAY [STRING_8]
			-- Long text representation of months
			-- (from DATE_CONSTANTS)
		do
			Result := Date_time_tools.Long_months_text
		end

	Max_weeks_in_year: INTEGER_32 = 53
			-- Maximun number of weeks in a year
			-- (from DATE_CONSTANTS)

	minute: INTEGER_32
			-- Minute of the current object
			-- (from DATE_TIME_MEASUREMENT)
		do
			Result := time.minute
		ensure -- from DATE_TIME_MEASUREMENT
			same_minute: Result = time.minute
		end

	Minutes_in_hour: INTEGER_32 = 60
			-- Number of minutes in an hour
			-- (from TIME_CONSTANTS)

	month: INTEGER_32
			-- Month of the current object
			-- (from DATE_TIME_MEASUREMENT)
		do
			Result := date.month
		ensure -- from DATE_TIME_MEASUREMENT
			same_month: Result = date.month
		end

	Months_in_year: INTEGER_32 = 12
			-- Number of months in year
			-- (from DATE_CONSTANTS)

	months_text: ARRAY [STRING_8]
			-- Short text representation of months
			-- (from DATE_CONSTANTS)
		do
			Result := Date_time_tools.Months_text
		end

	origin_date_time: detachable DATE_TIME
			-- Origin date time of duration

	second: INTEGER_32
			-- Second of the current object
			-- (from DATE_TIME_MEASUREMENT)
		do
			Result := time.second
		ensure -- from DATE_TIME_MEASUREMENT
			same_second: Result = time.second
		end

	seconds_count: INTEGER_64
			-- Total number of seconds of current duration
		require
			has_origin: has_origin_date_time
		do
			Result := (date.days_count.to_integer_64 * Seconds_in_day.to_integer_64) + time.seconds_count.to_integer_64
		end

	Seconds_in_day: INTEGER_32 = 86400
			-- Number of seconds in an hour
			-- (from TIME_CONSTANTS)

	Seconds_in_hour: INTEGER_32 = 3600
			-- Number of seconds in an hour
			-- (from TIME_CONSTANTS)

	Seconds_in_minute: INTEGER_32 = 60
			-- Number of seconds in a minute
			-- (from TIME_CONSTANTS)

	time: TIME_DURATION
			-- Time part of current duration

	time_default_format_string: STRING_8
			-- Default output format for times
			-- (from TIME_CONSTANTS)
		do
			Result := Date_time_tools.Time_default_format_string
		end

	year: INTEGER_32
			-- Year of the current object
			-- (from DATE_TIME_MEASUREMENT)
		do
			Result := date.year
		ensure -- from DATE_TIME_MEASUREMENT
			same_year: Result = date.year
		end

	zero: like Current
			-- Neutral element for "+" and "-"
		do
			create Result.make_by_date_time (date.zero, time.zero)
		ensure -- from GROUP_ELEMENT
			result_exists: Result /= Void
		end
	
feature -- Comparison

	frozen deep_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void
			-- or attached to isomorphic object structures?
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.is_deep_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			shallow_implies_deep: standard_equal (a, b) implies Result
			both_or_none_void: (a = Void) implies (Result = (b = Void))
			same_type: (Result and (a /= Void)) implies (b /= Void and then a.same_type (b))
			symmetric: Result implies deep_equal (b, a)
		end

	frozen equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void or attached
			-- to objects considered equal?
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.is_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.is_equal (b))
		end

	frozen is_deep_equal (other: DATE_TIME_DURATION): BOOLEAN
			-- Are Current and other attached to isomorphic object structures?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		ensure -- from ANY
			shallow_implies_deep: standard_is_equal (other) implies Result
			same_type: Result implies same_type (other)
			symmetric: Result implies other.is_deep_equal (Current)
		end

	is_equal (other: like Current): BOOLEAN
			-- Are the current duration an other equal?
		require -- from ANY
			other_not_void: other /= Void
		do
			Result := year = other.year and then month = other.month and then (day + time.to_days = other.day + other.time.to_days) and then time.time_modulo_day.is_equal (other.time.time_modulo_day)
		ensure -- from ANY
			symmetric: Result implies other ~ Current
			consistent: standard_is_equal (other) implies Result
		end

	is_greater alias ">" (other: DATE_TIME_DURATION): BOOLEAN
			-- Is current object greater than other?
			-- (from PART_COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		do
			Result := other < Current
		end

	is_greater_equal alias ">=" (other: DATE_TIME_DURATION): BOOLEAN
			-- Is current object greater than or equal to other?
			-- (from PART_COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		do
			Result := (other < Current) or (Current ~ other)
		end

	is_less alias "<" (other: like Current): BOOLEAN
			-- Is the current duration smaller than other?
			-- False if either is not definite
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		do
			if definite and then other.definite then
				Result := (day + time.to_days < other.day + other.time.to_days) or else (day + time.to_days = other.day + other.time.to_days) and then (time.time_modulo_day < other.time.time_modulo_day)
			end
		ensure then
			non_definite_result: not (definite and other.definite) implies not Result
		end

	is_less_equal alias "<=" (other: DATE_TIME_DURATION): BOOLEAN
			-- Is current object less than or equal to other?
			-- (from PART_COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		do
			Result := (Current < other) or (Current ~ other)
		end

	frozen standard_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void or attached to
			-- field-by-field identical objects of the same type?
			-- Always uses default object comparison criterion.
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.standard_is_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.standard_is_equal (b))
		end

	frozen standard_is_equal (other: DATE_TIME_DURATION): 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
		external
			"built_in"
		ensure -- from ANY
			same_type: Result implies same_type (other)
			symmetric: Result implies other.standard_is_equal (Current)
		end
	
feature -- Status report

	canonical (start_date: DATE_TIME): BOOLEAN
			-- Are the time and date parts of the same sign,
			-- and both canonical?
		require
			start_date_not_void: start_date /= Void
		local
			final_date: DATE_TIME
		do
			final_date := start_date + Current
			if final_date >= start_date then
				Result := date.canonical (start_date.date) and then time.seconds_count >= 0 and then time.canonical and then hour < Hours_in_day
			else
				Result := date.canonical (start_date.date) and then time.seconds_count <= 0 and then time.canonical and then hour > - Hours_in_day
			end
		end

	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
		external
			"built_in"
		end

	definite: BOOLEAN
			-- Is this duration date-independent?
			-- (True if it only uses day, not year and month)
		do
			Result := date.definite
		ensure
			result_definition: Result = (year = 0 and then month = 0)
		end

	has_origin_date_time: BOOLEAN
			-- Has an origin_date_time been set?
		do
			Result := attached origin_date_time
		end

	i_th_leap_year (i: INTEGER_32): BOOLEAN
		obsolete "Use `is_leap_year' instead. [2017-05-31]"
			-- (from DATE_CONSTANTS)
		do
			Result := is_leap_year (i)
		end

	is_leap_year (y: INTEGER_32): BOOLEAN
			-- Is year y a leap year?
			-- (from DATE_CONSTANTS)
		do
			Result := (mod (y, 4) = 0) and ((mod (y, 100) /= 0) or (mod (y, 400) = 0))
		end

	is_negative: BOOLEAN
			-- Is duration negative?
			-- (from DURATION)
		do
			Result := not is_positive and not is_zero
		end

	is_positive: BOOLEAN
			-- Is duration positive?
		do
			Result := (date.is_positive or date.is_zero) and (time.is_positive or time.is_zero) and not (date.is_zero and time.is_zero)
		end

	is_zero: BOOLEAN
			-- Is duration zero?
			-- (from DURATION)
		do
			Result := equal (Current, zero)
		end

	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
		external
			"built_in"
		ensure -- from ANY
			definition: Result = (conforms_to (other) and other.conforms_to (Current))
		end
	
feature -- Status setting

	set_origin_date_time (dt: detachable DATE_TIME)
			-- Set origin_date_time to dt.
		do
			origin_date_time := dt
			if dt /= Void then
				date.set_origin_date (dt.date)
			else
				date.set_origin_date (Void)
			end
		ensure
			origin_date_time_set: origin_date_time = dt
			origin_date_set: dt /= Void implies (dt.date = date.origin_date)
		end
	
feature -- Element change

	identity alias "+": DATE_TIME_DURATION
			-- Unary plus
			-- (from DURATION)
		do
			Result := deep_twin
		ensure -- from GROUP_ELEMENT
			result_exists: Result /= Void
			result_definition: Result.is_equal (Current)
		end

	minus alias "-" (other: DATE_TIME_DURATION): DATE_TIME_DURATION
			-- Difference with other
			-- (from DURATION)
		require -- from GROUP_ELEMENT
			other_exists: other /= Void
		do
			Result := Current + - other
		ensure -- from GROUP_ELEMENT
			result_exists: Result /= Void
		end
	
feature -- Conversion

	time_to_canonical: like Current
			-- A new duration, equivalent to current one
			-- but time is canonical and has the same sign as date
		require
			definite_duration: definite
		do
			Result := deep_twin
			if Current >= zero then
				if time < time.zero then
					Result.time.hour_add (- time.to_days * Hours_in_day)
				end
				Result.day_add (time.to_days)
				Result.set_time (Result.time.time_modulo_day)
			else
				Result := - (- Result).time_to_canonical
			end
		ensure
			time_canonical: Result.time.canonical
			same_sign: ((Result.date > date.zero) implies (Result.time >= time.zero)) and then ((Result.date < date.zero) implies (Result.time <= time.zero))
		end

	to_canonical (start_date: DATE_TIME): like Current
			-- A new duration, equivalent to current one
			-- and canonical for start_date
		local
			final_date: DATE_TIME
			date_part_of_result: DATE_DURATION
			time_part_of_result: TIME_DURATION
		do
			if canonical (start_date) then
				Result := deep_twin
			else
				final_date := start_date + Current
				create time_part_of_result.make_fine (final_date.hour - start_date.hour, final_date.minute - start_date.minute, final_date.fine_second - start_date.fine_second)
				if (final_date >= start_date) and then (final_date.time < start_date.time) then
					time_part_of_result.hour_add (24)
					final_date.day_add (-1)
				elseif (final_date < start_date) and then (final_date.time > start_date.time) then
					time_part_of_result.hour_add (-24)
					final_date.day_add (1)
				end
				create date_part_of_result.make_by_days (final_date.days - start_date.days)
				create Result.make_by_date_time (date_part_of_result.to_canonical (start_date.date), time_part_of_result.to_canonical)
			end
		ensure
			canonical_set: Result.canonical (start_date)
			duration_not_changed: equal (start_date + Current, start_date + Result)
		end
	
feature -- Duplication

	frozen clone (other: detachable ANY): like other
		obsolete "Use `twin' instead. [2017-05-31]"
			-- Void if other is void; otherwise new object
			-- equal to other
			--
			-- For non-void other, clone calls copy;
			-- to change copying/cloning semantics, redefine copy.
			-- (from ANY)
		do
			if other /= Void then
				Result := other.twin
			end
		ensure -- from ANY
			instance_free: class
			equal: Result ~ other
		end

	copy (other: DATE_TIME_DURATION)
			-- 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)
		external
			"built_in"
		ensure -- from ANY
			is_equal: Current ~ other
		end

	frozen deep_clone (other: detachable ANY): like other
		obsolete "Use `deep_twin' instead. [2017-05-31]"
			-- Void if other is void: otherwise, new object structure
			-- recursively duplicated from the one attached to other
			-- (from ANY)
		do
			if other /= Void then
				Result := other.deep_twin
			end
		ensure -- from ANY
			instance_free: class
			deep_equal: deep_equal (other, Result)
		end

	frozen deep_copy (other: DATE_TIME_DURATION)
			-- Effect equivalent to that of:
			--		copy (other . deep_twin)
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		do
			copy (other.deep_twin)
		ensure -- from ANY
			deep_equal: deep_equal (Current, other)
		end

	frozen deep_twin: DATE_TIME_DURATION
			-- New object structure recursively duplicated from Current.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			deep_twin_not_void: Result /= Void
			deep_equal: deep_equal (Current, Result)
		end

	frozen standard_clone (other: detachable ANY): like other
		obsolete "Use `standard_twin' instead. [2017-05-31]"
			-- Void if other is void; otherwise new object
			-- field-by-field identical to other.
			-- Always uses default copying semantics.
			-- (from ANY)
		do
			if other /= Void then
				Result := other.standard_twin
			end
		ensure -- from ANY
			instance_free: class
			equal: standard_equal (Result, other)
		end

	frozen standard_copy (other: DATE_TIME_DURATION)
			-- 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)
		external
			"built_in"
		ensure -- from ANY
			is_standard_equal: standard_is_equal (other)
		end

	frozen standard_twin: DATE_TIME_DURATION
			-- New object field-by-field identical to other.
			-- Always uses default copying semantics.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			standard_twin_not_void: Result /= Void
			equal: standard_equal (Result, Current)
		end

	frozen twin: DATE_TIME_DURATION
			-- New object equal to Current
			-- twin calls copy; to change copying/twinning semantics, redefine copy.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			twin_not_void: Result /= Void
			is_equal: Result ~ Current
		end
	
feature -- Basic operations

	frozen as_attached: attached DATE_TIME_DURATION
		obsolete "Remove calls to this feature. [2017-05-31]"
			-- Attached version of Current.
			-- (Can be used during transitional period to convert
			-- non-void-safe classes to void-safe ones.)
			-- (from ANY)
		do
			Result := Current
		end

	day_add (d: INTEGER_32)
			-- Add d days to the current duration.
		do
			date.set_day (day + d)
		ensure
			result_definition: day = old day + d
		end

	frozen default: detachable DATE_TIME_DURATION
			-- Default value of object's type
			-- (from ANY)
		do
		end

	frozen default_pointer: POINTER
			-- Default value of type POINTER
			-- (Avoid the need to write p.default for
			-- some p of type POINTER.)
			-- (from ANY)
		do
		ensure -- from ANY
			instance_free: class
		end

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

	frozen do_nothing
			-- Execute a null action.
			-- (from ANY)
		do
		ensure -- from ANY
			instance_free: class
		end

	opposite alias "-": like Current
			-- Unary minus
		require -- from  GROUP_ELEMENT
			True
		local
			l_origin: like origin_date_time
		do
			create Result.make_by_date_time (- date, - time)
			l_origin := origin_date_time
			if l_origin /= Void then
				Result.set_origin_date_time (l_origin.twin)
			else
				Result.set_origin_date_time (Void)
			end
		ensure -- from GROUP_ELEMENT
			result_exists: Result /= Void
			result_definition: (Result + Current).is_equal (zero)
		ensure then
			origin_date_time: equal (origin_date_time, Result.origin_date_time)
		end

	plus alias "+" (other: like Current): like Current
			-- Sum with other (commutative)
		require -- from GROUP_ELEMENT
			other_exists: other /= Void
		local
			l_origin: like origin_date_time
		do
			create Result.make_by_date_time (date + other.date, time + other.time)
			l_origin := origin_date_time
			if l_origin /= Void then
				Result.set_origin_date_time (l_origin.twin)
			else
				Result.set_origin_date_time (Void)
			end
		ensure -- from GROUP_ELEMENT
			result_exists: Result /= Void
			commutative: Result.is_equal (other + Current)
		ensure then
			origin_date_time: equal (origin_date_time, Result.origin_date_time)
		end
	
feature {NONE} -- Basic operations

	div (i, j: INTEGER_32): INTEGER_32
			-- (i \\ j) if i positive
			-- (i \\ j + 1) if i negative
			-- (from TIME_UTILITY)
		do
			Result := i // j
			if Result.to_double > i / j then
				Result := Result - 1
			end
		ensure -- from TIME_UTILITY
			result_definition: i = j * Result + mod (i, j)
		end

	mod (i, j: INTEGER_32): INTEGER_32
			-- (i \\ j) if i positive
			-- (i \\ j + j) if i negative
			-- (from TIME_UTILITY)
		do
			Result := i \\ j
			if Result < 0 then
				Result := Result + j
			end
		ensure -- from TIME_UTILITY
			positive_result: Result >= 0
			result_definition: i = j * div (i, j) + Result
		end
	
feature {NONE} -- Implementation

	Days_in_months: ARRAY [INTEGER_32]
			-- Array containing number of days for each month of
			-- a non-leap year.
			-- (from DATE_CONSTANTS)
		once
			Result := <<31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31>>
		ensure -- from DATE_CONSTANTS
			result_exists: Result /= Void
			valid_count: Result.count = Months_in_year
		end
	
feature -- Element Change

	set_date (d: DATE_DURATION)
			-- Set date to d.
		require
			d_exists: d /= Void
		do
			date := d
		ensure
			date_set: date = d
		end

	set_time (t: TIME_DURATION)
			-- Set time to t.
		require
			t_exists: time /= Void
		do
			time := t
		ensure
			time_set: time = t
		end
	
feature -- Output

	Io: STD_FILES
			-- Handle to standard file setup
			-- (from ANY)
		once
			create Result
			Result.set_output_default
		ensure -- from ANY
			instance_free: class
			io_not_void: Result /= Void
		end

	out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from ANY)
		do
			Result := tagged_out
		ensure -- from ANY
			out_not_void: Result /= Void
		end

	print (o: detachable ANY)
			-- Write terse external representation of o
			-- on standard output.
			-- (from ANY)
		do
			if o /= Void then
				Io.put_string (o.out)
			end
		ensure -- from ANY
			instance_free: class
		end

	frozen tagged_out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			tagged_out_not_void: Result /= Void
		end
	
feature -- Platform

	Operating_environment: OPERATING_ENVIRONMENT
			-- Objects available from the operating system
			-- (from ANY)
		once
			create Result
		ensure -- from ANY
			instance_free: class
			operating_environment_not_void: Result /= Void
		end
	
feature {NONE} -- Retrieval

	frozen internal_correct_mismatch
			-- Called from runtime to perform a proper dynamic dispatch on correct_mismatch
			-- from MISMATCH_CORRECTOR.
			-- (from ANY)
		local
			l_msg: STRING_8
			l_exc: EXCEPTIONS
		do
			if attached {MISMATCH_CORRECTOR} Current as l_corrector then
				l_corrector.correct_mismatch
			else
				create l_msg.make_from_string ("Mismatch: ")
				create l_exc
				l_msg.append (generating_type.name)
				l_exc.raise_retrieval_exception (l_msg)
			end
		end
	
invariant
	date_exists: date /= Void
	time_exists: time /= Void
	origin_constraint: (origin_date_time = Void and date.origin_date = Void) or else (attached origin_date_time as l_origin_1 and then l_origin_1.date = date.origin_date)
	same_signs: (has_origin_date_time and then attached origin_date_time as l_origin_2 and then canonical (l_origin_2)) implies ((date.is_positive or date.is_zero) and (time.is_positive or time.is_zero)) or else ((date.is_negative or date.is_zero) and (time.is_negative or time.is_zero))

		-- from DURATION
	sign_correctness: is_positive xor is_negative xor is_zero

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

		-- from GROUP_ELEMENT
	neutral_addition: is_equal (Current + zero)
	self_subtraction: zero.is_equal (Current - Current)

		-- from DATE_TIME_MEASUREMENT
	date_exists: date /= Void
	time_exists: time /= Void

note
	copyright: "Copyright (c) 1984-2017, Eiffel Software and others"
	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
	source: "[
		Eiffel Software
		5949 Hollister Ave., 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 DATE_TIME_DURATION

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