note
	description: "Absolute dates"
	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 $"
	access: date
	eis: "name=DATE / TIME to STRING Conversion", "src=$(ISE_DOC_UUID)/88972ba4-694b-8558-b0c8-87b1fc40afc4", "tag=EiffelTime"
	eis: "name=Obtaining a DATE from a DATE_TIME and vice versa", "src=$(ISE_DOC_UUID)/195849fc-1a9c-d734-2d2b-acae78133886#Obtaining_a_DATE_from_a_DATE_TIME_and_vice_versa", "tag=EiffelTime"

class 
	DATE

create 
	make,
	make_month_day_year,
	make_day_month_year,
	make_now,
	make_now_utc,
	make_by_days,
	make_from_string_default,
	make_from_string_default_with_base,
	make_from_string,
	make_from_string_with_base,
	make_by_compact_date,
	make_by_ordered_compact_date

feature -- Initialization

	make (y, m, d: INTEGER_32)
			-- Set year, month and day to y, m, d respectively.
		require
			correct_date: is_correct_date (y, m, d)
		do
			set_date (y, m, d)
		ensure
			year_set: year = y
			month_set: month = m
			day_set: day = d
		end

	make_by_compact_date (c_d: INTEGER_32)
		obsolete "Use `make_by_ordered_compact_date' instead. But be careful in your update since `compact_date' and `ordered_compact_date' do not have the same encoding. [2017-05-31]"
			-- Initialize from a compact_date.
		require
			c_d_valid: compact_date_valid (c_d)
		do
			set_private_internal_compact_date (c_d)
		ensure
			compact_date_set: year | (month |<< 16) | (day |<< 24) = c_d
		end

	make_by_days (n: INTEGER_32)
			-- Set the current date with the number of days n since Origin.
		local
			i, j: INTEGER_32
			y, m, d: INTEGER_32
		do
			i := 4 * (n - 59) - 1
			j := 4 * div (mod (i, 146097), 4) + 3
			y := 100 * div (i, 146097) + div (j, 1461)
			i := 5 * div (mod (j, 1461) + 4, 4) - 3
			m := div (i, 153)
			d := div (mod (i, 153) + 5, 5)
			if m < 10 then
				m := m + 3
			else
				m := m - 9
				y := y + 1
			end
			y := y + 1600
			make (y, m, d)
		ensure
			days_set: days = n
		end

	make_by_ordered_compact_date (c_d: INTEGER_32)
			-- Initialize from a ordered_compact_date.
		require
			c_d_valid: ordered_compact_date_valid (c_d)
		do
			set_internal_ordered_compact_date (c_d)
		ensure
			ordered_compact_date_set: ordered_compact_date = c_d
		end

	make_day_month_year (d, m, y: INTEGER_32)
			-- Set day, month and year to d, m and y respectively.
		require
			correct_date: is_correct_date (y, m, d)
		do
			make (y, m, d)
		ensure
			year_set: year = y
			month_set: month = m
			day_set: day = d
		end

	make_from_string (s: STRING_8; code: STRING_8)
			-- Initialize from a "standard" string of form
			-- code.
			-- (For 2-digit year specifications, the current century is used as
			-- base century.)
		require
			s_exists: s /= Void
			c_exists: code /= Void
			date_valid: date_valid (s, code)
		local
			date: DATE
		do
			date := (create {DATE_TIME_CODE_STRING}.make (code)).create_date (s)
			make (date.year, date.month, date.day)
		end

	make_from_string_default (s: STRING_8)
			-- Initialize from a "standard" string of form
			-- date_default_format_string.
			-- (For 2-digit year specifications, the current century is used as
			-- base century.)
		require
			s_exists: s /= Void
			date_valid: date_valid (s, date_default_format_string)
		do
			make_from_string (s, date_default_format_string)
		end

	make_from_string_default_with_base (s: STRING_8; base: INTEGER_32)
			-- Initialize from a "standard" string of form
			-- date_default_format_string with base century base.
		require
			s_exists: s /= Void
			base_valid: base > 0 and (base \\ 100 = 0)
			date_valid: date_valid_with_base (s, date_default_format_string, base)
		do
			make_from_string_with_base (s, date_default_format_string, base)
		end

	make_from_string_with_base (s: STRING_8; code: STRING_8; base: INTEGER_32)
			-- Initialize from a "standard" string of form
			-- code with base century base.
		require
			s_exists: s /= Void
			c_exists: code /= Void
			base_valid: base > 0 and (base \\ 100 = 0)
			date_valid: date_valid_with_base (s, code, base)
		local
			code_string: DATE_TIME_CODE_STRING
			date: DATE
		do
			create code_string.make (code)
			code_string.set_base_century (base)
			date := code_string.create_date (s)
			make (date.year, date.month, date.day)
		end

	make_month_day_year (m, d, y: INTEGER_32)
			-- Set month, day and year to m, d and y respectively.
		require
			correct_date: is_correct_date (y, m, d)
		do
			make (y, m, d)
		ensure
			year_set: year = y
			month_set: month = m
			day_set: day = d
		end

	make_now
			-- Set the current object to today's date.
		local
			l_date: C_DATE
		do
			create l_date
			make (l_date.year_now, l_date.month_now, l_date.day_now)
		end

	make_now_utc
			-- Set the current object to today's date in utc format.
		local
			l_date: C_DATE
		do
			create l_date.make_utc
			make (l_date.year_now, l_date.month_now, l_date.day_now)
		end
	
feature {NONE} -- Initialization

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

	compact_date: INTEGER_32
		obsolete "Use `ordered_compact_date' instead. But be careful in your update since `compact_date' and `ordered_compact_date' do not have the same encoding. [2017-05-31]"
			-- Day, month and year coded.
			-- (from DATE_VALUE)
		do
			Result := year | (month |<< 16) | (day |<< 24)
		end

	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_VALUE)
		do
			Result := ordered_compact_date & Day_mask
		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

	generating_type: TYPE [detachable DATE]
			-- 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

	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)

	month: INTEGER_32
			-- Month of the current object
			-- (from DATE_VALUE)
		do
			Result := (ordered_compact_date & Month_mask) |>> Month_shift
		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

	ordered_compact_date: INTEGER_32
			-- Year, month, day coded for fast comparison between dates.
			-- (from DATE_VALUE)

	Origin: DATE
			-- Origin date
		once
			create Result.make (1600, 1, 1)
		ensure -- from ABSOLUTE
			result_exists: Result /= Void
		end

	year: INTEGER_32
			-- Year of the current object
			-- (from DATE_VALUE)
		do
			Result := ((ordered_compact_date & Year_mask) |>> Year_shift) & 65535
		end
	
feature -- Measurement

	days: INTEGER_32
			-- Number of days elapsed since Origin
		do
			Result := days_from (Origin.year) + year_day - Origin.year_day
		ensure
			same_duration: Result = duration.day
		end

	duration: DATE_DURATION
			-- Definite duration elapsed since Origin
		require -- from  ABSOLUTE
			True
		do
			create Result.make_by_days (days_from (Origin.year) + year_day - Origin.year_day)
		ensure then
			definite_result: Result.definite
			duration_set: ((Current - Origin).duration).is_equal (Result)
		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): 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: DATE): 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
		do
			Result := not (Current < other) and not (other < Current)
		ensure -- from ANY
			symmetric: Result implies other ~ Current
			consistent: standard_is_equal (other) implies Result
		ensure then -- from COMPARABLE
			trichotomy: Result = (not (Current < other) and not (other < Current))
		end

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

	is_greater_equal alias ">=" (other: DATE): BOOLEAN
			-- Is current object greater than or equal to other?
			-- (from COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		do
			Result := not (Current < other)
		ensure then -- from COMPARABLE
			definition: Result = (other <= Current)
		end

	is_less alias "<" (other: like Current): BOOLEAN
			-- Is the current date before other?
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		local
			l_current, l_other: INTEGER_32
		do
			l_current := ordered_compact_date
			l_other := other.ordered_compact_date
			if l_current >= 0 and l_other >= 0 then
				Result := l_current < l_other
			else
				Result := year < other.year and (l_current & 65535) < (l_other & 65535)
			end
		ensure then -- from COMPARABLE
			asymmetric: Result implies not (other < Current)
		end

	is_less_equal alias "<=" (other: DATE): BOOLEAN
			-- Is current object less than or equal to other?
			-- (from COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		do
			Result := not (other < Current)
		ensure then -- from COMPARABLE
			definition: Result = ((Current < other) or (Current ~ other))
		end

	max (other: DATE): DATE
			-- The greater of current object and other
			-- (from COMPARABLE)
		require -- from COMPARABLE
			other_exists: other /= Void
		do
			if Current >= other then
				Result := Current
			else
				Result := other
			end
		ensure -- from COMPARABLE
			current_if_not_smaller: Current >= other implies Result = Current
			other_if_smaller: Current < other implies Result = other
		end

	min (other: DATE): DATE
			-- The smaller of current object and other
			-- (from COMPARABLE)
		require -- from COMPARABLE
			other_exists: other /= Void
		do
			if Current <= other then
				Result := Current
			else
				Result := other
			end
		ensure -- from COMPARABLE
			current_if_not_greater: Current <= other implies Result = Current
			other_if_greater: Current > other implies Result = 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): 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

	three_way_comparison (other: DATE): INTEGER_32
			-- If current object equal to other, 0;
			-- if smaller, -1; if greater, 1
			-- (from COMPARABLE)
		require -- from COMPARABLE
			other_exists: other /= Void
		do
			if Current < other then
				Result := -1
			elseif other < Current then
				Result := 1
			end
		ensure -- from COMPARABLE
			equal_zero: (Result = 0) = (Current ~ other)
			smaller_negative: (Result = -1) = (Current < other)
			greater_positive: (Result = 1) = (Current > other)
		end
	
feature -- Status report

	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

	day_of_january_1st: INTEGER_32
			-- Day of the week of january 1st of the current year
		do
			Result := (create {DATE}.make (year, 1, 1)).day_of_the_week
		ensure
			day_of_the_week_definition: Result > 0 and then Result < 8
		end

	day_of_the_week: INTEGER_32
			-- Number of day from the beginning of the week
			-- sunday is 1, etc.., saturday is 7
		do
			Result := mod (days - 1, 7) + 1
		ensure
			day_of_the_week_range: Result > 0 and then Result < 8
		end

	days_at_month: INTEGER_32
			-- Number of days from the beginning of the year
			-- until the beginning of the current month
		local
			l_month: INTEGER_32
		do
			l_month := month
			Result := Days_at_months @ l_month
			if l_month > 2 and then leap_year then
				Result := Result + 1
			end
		ensure
			positive_result: Result >= 0
		end

	days_from (y: INTEGER_32): INTEGER_32
			-- Days between the current year and year y
		local
			l_year: like year
		do
			l_year := year
			Result := (l_year - y) * Days_in_non_leap_year + (div (l_year - 1, 4) - div (y - 1, 4)) - (div (l_year - 1, 100) - div (y - 1, 100)) + (div (l_year - 1, 400) - div (y - 1, 400))
		end

	days_in_year: INTEGER_32
			-- Number of days in the current year
		do
			if leap_year then
				Result := Days_in_leap_year
			else
				Result := Days_in_non_leap_year
			end
		ensure
			valid_result: (leap_year implies Result = Days_in_leap_year) and then (not leap_year implies Result = Days_in_non_leap_year)
		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

	leap_year: BOOLEAN
			-- Is the current year a leap year?
		do
			Result := is_leap_year (year)
		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

	week_of_year: INTEGER_32
			-- Number of weeks from the beginning of the year
			-- The first week of the year begins on the first sunday of the year
			-- The week number before the first sunday of the year is 0
		do
			if day_of_the_week <= year_day then
				if day_of_january_1st > 0 then
					Result := div (year_day - day_of_the_week, Days_in_week) + 1
				else
					Result := div (year_day - day_of_the_week + day_of_january_1st - 1, Days_in_week)
				end
			else
				Result := 0
			end
		ensure
			positive_result: Result >= 0
			result_small_enough: Result < Max_weeks_in_year
		end

	year_day: INTEGER_32
			-- Number of days from the beginning of the year
		do
			Result := days_at_month + day
		ensure
			result_large_enough: Result >= 1
			result_small_enough: Result <= days_in_year
		end
	
feature -- Element change

	set_date (y, m, d: INTEGER_32)
			-- Set year with y, month with m and day with d.
			-- (from DATE_VALUE)
		require -- from DATE_MEASUREMENT
			d_large_enough: d >= 1
			m_large_enough: m >= 1
			m_small_enough: m <= Months_in_year
			d_small_enough: d <= days_in_i_th_month (m, y)
		local
			l_date: like ordered_compact_date
		do
			l_date := l_date & Day_mask.bit_not
			l_date := l_date | d
			l_date := l_date & Month_mask.bit_not
			l_date := l_date | (m |<< Month_shift)
			l_date := l_date & Year_mask.bit_not
			l_date := l_date | (y |<< Year_shift)
			ordered_compact_date := l_date
		ensure -- from DATE_MEASUREMENT
			day_set: day = d
			month_set: month = m
			year_set: year = y
		end

	set_day (d: INTEGER_32)
			-- Set day to d.
			-- (from DATE_VALUE)
		require -- from DATE_MEASUREMENT
			d_large_enough: d >= 1
			d_small_enough: d <= days_in_month
		local
			l_date: like ordered_compact_date
		do
			l_date := ordered_compact_date
			l_date := l_date & Day_mask.bit_not
			l_date := l_date | d
			ordered_compact_date := l_date
		ensure -- from DATE_MEASUREMENT
			day_set: day = d
		end

	set_internal_compact_date (a_compact_date: like compact_date)
		obsolete "Use `ordered_compact_date' instead. But be careful in your update since `compact_date' and `ordered_compact_date' do not have the same encoding. [2017-05-31]"
			-- Set a_compact_date to compact_date.
			-- (from DATE_VALUE)
		do
			set_private_internal_compact_date (a_compact_date)
		ensure -- from DATE_VALUE
			compact_date_set: year | (month |<< 16) | (day |<< 24) = a_compact_date
		end

	set_internal_ordered_compact_date (a_ordered_compact_date: like ordered_compact_date)
			-- Set a_ordered_compact_date to ordered_compact_date.
			-- (from DATE_VALUE)
		do
			ordered_compact_date := a_ordered_compact_date
		ensure -- from DATE_VALUE
			ordered_compact_date_set: ordered_compact_date = a_ordered_compact_date
		end

	set_month (m: INTEGER_32)
			-- Set month to m.
			-- (from DATE_VALUE)
		require -- from DATE_MEASUREMENT
			m_large_enough: m >= 1
			m_small_enough: m <= Months_in_year
			d_small_enough: day <= days_in_i_th_month (m, year)
		local
			l_date: like ordered_compact_date
		do
			l_date := ordered_compact_date
			l_date := l_date & Month_mask.bit_not
			l_date := l_date | (m |<< Month_shift)
			ordered_compact_date := l_date
		ensure -- from DATE_MEASUREMENT
			month_set: month = m
		end

	set_year (y: INTEGER_32)
			-- Set year to y.
			-- (from DATE_VALUE)
		require -- from DATE_MEASUREMENT
			can_not_cut_29th_feb: day <= days_in_i_th_month (month, y)
		local
			l_date: like ordered_compact_date
		do
			l_date := ordered_compact_date
			l_date := l_date & Year_mask.bit_not
			l_date := l_date | (y |<< Year_shift)
			ordered_compact_date := l_date
		ensure -- from DATE_MEASUREMENT
			year_set: year = y
		end
	
feature -- Conversion

	to_date_time: DATE_TIME
			-- Date-time version, with a zero time component
		do
			create Result.make_by_date (Current)
		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)
			-- 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)
			-- 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
			-- 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)
			-- 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
			-- 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
			-- 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

	add (d: DATE_DURATION)
			-- Adds d to the current date.
			-- if d is not definite, add years and months and then days.
		require
			d_not_void: d /= Void
		do
			if d.definite then
				day_add (d.day)
			else
				year_month_add (d.year, d.month)
				day_add (d.day)
			end
		end

	frozen as_attached: attached DATE
		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 date.
		do
			make_by_days (days + d)
		ensure
			days_set: days = old days + d
		end

	day_back
			-- Move to previous day.
		do
			if day = 1 then
				month_back
				set_day (days_in_month)
			else
				set_day (day - 1)
			end
		ensure
			days_set: days = old days - 1
		end

	day_forth
			-- Move to next day.
			-- days is from the origin, day is current.
		do
			if day = days_in_month then
				set_day (1)
				month_forth
			else
				set_day (day + 1)
			end
		ensure
			days_set: days = old days + 1
		end

	frozen default: detachable DATE
			-- 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

	minus alias "-" (other: DATE): INTERVAL [DATE]
			-- Interval between current object and other.
			-- (from ABSOLUTE)
		require -- from ABSOLUTE
			other_exists: other /= Void
			other_smaller_than_current: other <= Current
		do
			create Result.make (other, Current)
		ensure -- from ABSOLUTE
			result_exists: Result /= Void
			result_set: Result.start_bound.is_equal (other) and then Result.end_bound.is_equal (Current)
		end

	month_add (m: INTEGER_32)
			-- Add m months to the current date.
			-- Can move days backward.
		local
			new_month, new_year: INTEGER_32
			days_in_new_month: INTEGER_32
			l_old_month, l_old_day: INTEGER_32
		do
			l_old_month := month
			new_month := mod ((l_old_month + m - 1), Months_in_year) + 1
			new_year := year + div ((l_old_month + m - 1), Months_in_year)
			days_in_new_month := days_in_i_th_month (new_month, new_year)
			l_old_day := day
			if l_old_day > days_in_new_month then
				set_date (new_year, new_month, days_in_new_month)
			else
				set_date (new_year, new_month, l_old_day)
			end
		end

	month_back
			-- Move to previous month.
			-- Can move days backward if previous month has less days than the
			-- current month.
		local
			days_in_new_month: INTEGER_32
		do
			if month = 1 then
				set_month (Months_in_year)
				year_back
			else
				days_in_new_month := days_in_i_th_month (month - 1, year)
				if day > days_in_new_month then
					set_day (days_in_new_month)
				end
				set_month (month - 1)
			end
		end

	month_forth
			-- Move to next month.
			-- Can move days backward if next month has less days than the
			-- current month.
		local
			days_in_new_month: INTEGER_32
		do
			if month = Months_in_year then
				set_month (1)
				year_forth
			else
				days_in_new_month := days_in_i_th_month (month + 1, year)
				if day > days_in_new_month then
					set_day (days_in_new_month)
				end
				set_month (month + 1)
			end
		end

	plus alias "+" (d: DATE_DURATION): DATE
			-- Sum to current date the duration d
			-- if duration not define, add years and then months and then days.
		require
			d_not_void: d /= Void
		do
			Result := twin
			Result.add (d)
		ensure
			result_exists: Result /= Void
			definite_set: d.definite implies (Result - Current).duration.is_equal (d)
		end

	relative_duration (other: like Current): DATE_DURATION
			-- Duration from other to the current date
		require -- from ABSOLUTE
			other_exists: other /= Void
		do
			create Result.make_by_days (days - other.days)
			Result := Result.to_canonical (other)
			Result.set_origin_date (other.twin)
		ensure -- from ABSOLUTE
			result_exists: Result /= Void
		ensure then
			exact_duration: (other + Result).is_equal (Current)
			canonical_duration: Result.canonical (other)
			origin_date_set: equal (Result.origin_date, other)
		end

	year_add (y: INTEGER_32)
			-- Add y years to the current date.
			-- May cut the 29th february.
		do
			if day > days_in_i_th_month (month, year + y) then
				set_day (days_in_i_th_month (month, year + y))
			end
			set_year (year + y)
		ensure
			year_set: year = old year + y
		end

	year_back
			-- Move to previous year.
			-- May cut the 29th february.
		do
			if day > days_in_i_th_month (month, year - 1) then
				set_day (days_in_i_th_month (month, year - 1))
			end
			set_year (year - 1)
		ensure
			year_decreased: year = old year - 1
		end

	year_forth
			-- Move to next year.
			-- May cut the 29th february.
		local
			l_year, l_month: INTEGER_32
			l_days_in_month: INTEGER_32
		do
			l_month := month
			l_year := year
			l_days_in_month := days_in_i_th_month (l_month, l_year + 1)
			if day > l_days_in_month then
				set_day (l_days_in_month)
			end
			set_year (l_year + 1)
		ensure
			year_increased: year = old year + 1
		end

	year_month_add (y, m: INTEGER_32)
			-- Add y years and m months to the current date.
			-- Check the number of days after.
		do
			month_add (y * Months_in_year + m)
		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

	Compact_date_attribute_name: STRING_8 = "compact_date"
			-- Name of compacte_date attribute in 5.3 and older version.
			-- (from DATE_VALUE)

	Day_mask: INTEGER_32 = 255
			-- (from DATE_VALUE)

	Day_shift: INTEGER_32 = 0
			-- Shift needed to extract/set year, month and day.
			-- (from DATE_VALUE)

	Days_at_months: SPECIAL [INTEGER_32]
			-- Array containing number of days from the end of
			-- the year to each month of a non-leap year
		once
			Result := (<<0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334>>).area
		ensure
			result_exists: Result /= Void
			count_is_months_in_year: Result.count - 1 = Months_in_year
		end

	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

	Month_mask: INTEGER_32 = 65280
			-- (from DATE_VALUE)

	Month_shift: INTEGER_32 = 8
			-- (from DATE_VALUE)

	set_private_internal_compact_date (a_compact_date: like compact_date)
			-- Set a_compact_date to compact_date.
			-- (from DATE_VALUE)
		do
			set_date (a_compact_date & 65535, (a_compact_date & 16711680) |>> 16, ((a_compact_date & 4278190080) |>> 24) & 255)
		ensure -- from DATE_VALUE
			compact_date_set: year | (month |<< 16) | (day |<< 24) = a_compact_date
		end

	Year_mask: INTEGER_32 = 4294901760
			-- Mask used to extract/set year, month and day.
			-- (from DATE_VALUE)

	Year_shift: INTEGER_32 = 16
			-- (from DATE_VALUE)
	
feature -- Correction

	correct_mismatch
			-- Attempt to correct object mismatch using Mismatch_information.
			-- (from DATE_VALUE)
		do
			if attached {INTEGER_32_REF} Mismatch_information.item (Compact_date_attribute_name) as l_compact_date then
				set_private_internal_compact_date (l_compact_date.item)
			else
				Precursor {MISMATCH_CORRECTOR}
			end
		end

	Mismatch_information: MISMATCH_INFORMATION
			-- Original attribute values of mismatched object
			-- (from MISMATCH_CORRECTOR)
		once
			create Result
		end
	
feature -- Output

	debug_output: STRING_8
			-- Printable representation of Current with "standard"
			-- Form: date_default_format_string
			-- Was declared in DATE as synonym of out.
		do
			Result := formatted_out (date_default_format_string)
		ensure -- from DEBUG_OUTPUT
			result_not_void: Result /= Void
		end

	formatted_out (s: STRING_8): STRING_8
			-- Printable representation of Current with "standard"
			-- Form: s
		require
			s_exists: s /= Void
		do
			Result := (create {DATE_TIME_CODE_STRING}.make (s)).create_date_string (Current)
		end

	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
			-- Printable representation of Current with "standard"
			-- Form: date_default_format_string
			-- Was declared in DATE as synonym of debug_output.
		do
			Result := formatted_out (date_default_format_string)
		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 -- Preconditions

	compact_date_valid (c_d: INTEGER_32): BOOLEAN
			-- Is compact date c_d valid?
			-- (from DATE_VALIDITY_CHECKER)
		local
			l_cd: INTEGER_32
			y, m, d: INTEGER_32
		do
			l_cd := ordered_compact_date
			set_private_internal_compact_date (c_d)
			d := day
			m := month
			y := year
			ordered_compact_date := l_cd
			Result := is_correct_date (y, m, d)
		end

	date_valid (s: STRING_8; code_string: STRING_8): BOOLEAN
			-- Is the code_string enough precise
			-- To create an instance of type DATE
			-- And does the string s correspond to code_string?
			-- (from DATE_VALIDITY_CHECKER)
		require -- from DATE_VALIDITY_CHECKER
			s_exists: s /= Void
			code_exists: code_string /= Void
		local
			code: DATE_TIME_CODE_STRING
		do
			create code.make (code_string)
			Result := code.precise_date and code.correspond (s) and then code.is_date (s)
		end

	date_valid_default (s: STRING_8): BOOLEAN
			-- Is the code_string enough precise
			-- To create an instance of type DATE
			-- And does the string s correspond to
			-- date_default_format_string?
			-- (from DATE_VALIDITY_CHECKER)
		require -- from DATE_VALIDITY_CHECKER
			s_exists: s /= Void
		do
			Result := date_valid (s, date_default_format_string)
		end

	date_valid_default_with_base (s: STRING_8; base: INTEGER_32): BOOLEAN
			-- Is the code_string enough precise
			-- To create an instance of type DATE
			-- And does the string s correspond to
			-- date_default_format_string?
			-- Use base century base.
			-- (from DATE_VALIDITY_CHECKER)
		require -- from DATE_VALIDITY_CHECKER
			s_exists: s /= Void
			base_valid: base > 0 and (base \\ 100 = 0)
		do
			Result := date_valid_with_base (s, date_default_format_string, base)
		end

	date_valid_with_base (s: STRING_8; code_string: STRING_8; base: INTEGER_32): BOOLEAN
			-- Is the code_string enough precise
			-- To create an instance of type DATE
			-- And does the string s correspond to code_string?
			-- Use base century base.
			-- (from DATE_VALIDITY_CHECKER)
		require -- from DATE_VALIDITY_CHECKER
			s_exists: s /= Void
			code_exists: code_string /= Void
			base_valid: base > 0 and (base \\ 100 = 0)
		local
			code: DATE_TIME_CODE_STRING
		do
			create code.make (code_string)
			code.set_base_century (base)
			Result := code.precise_date and code.correspond (s) and then code.is_date (s)
		end

	is_correct_date (y, m, d: INTEGER_32): BOOLEAN
			-- Is date specified by y, m, and d a correct date?
			-- (from DATE_VALIDITY_CHECKER)
		do
			Result := m >= 1 and m <= Months_in_year and then d >= 1 and d <= days_in_i_th_month (m, y) and then y >= 0 and then y <= 65535
		end

	ordered_compact_date_valid (c_d: INTEGER_32): BOOLEAN
			-- Is compact date c_d valid?
			-- (from DATE_VALIDITY_CHECKER)
		local
			l_cd: INTEGER_32
			y, m, d: INTEGER_32
		do
			l_cd := ordered_compact_date
			ordered_compact_date := c_d
			d := day
			m := month
			y := year
			ordered_compact_date := l_cd
			Result := is_correct_date (y, m, d)
		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
	
feature -- Status Report

	days_in_month: INTEGER_32
			-- Number of days in month 'month'.
			-- (from DATE_MEASUREMENT)
		do
			Result := days_in_i_th_month (month, year)
		ensure -- from DATE_MEASUREMENT
			positive_result: Result > 0
		end
	
invariant
	day_large_enough: day >= 1
	day_small_enough: day <= days_in_month
	month_large_enough: month >= 1
	month_small_enough: month <= Months_in_year
	year_small_enough: year <= 65535
	year_non_negative: year >= 0

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

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

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

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