indexing
	description: "Duration of dates and times"
	status: "See notice at end of class"
	date: "$Date$"
	revision: "$Revision$"
	access: date, time

class interface
	DATE_TIME_DURATION

create 

	make (y, mo, d, h, mi, s: INTEGER)
			-- Set year, month, day to y, mo, d.
			-- Set hour, minute, second to 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

	make_definite (d, h, m, s: INTEGER)
			-- Set day to d.
			-- Set hour, minute, second to 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

	make_fine (y, mo, d, h, mi: INTEGER; s: DOUBLE)
			-- set year, month, day to y, mo, d.
			-- set hour, minute, second to 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

	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
		ensure
			date_set: date = d
			time_set: time = t

	make_by_date (d: DATE_DURATION)
			-- Set date to d and time to zero.
		require
			d_exists: d /= void
		ensure
			date_set: date = d
			time_exists: time /= void
			time_set: time.is_equal (time.zero)

feature -- Initialization

	make (y, mo, d, h, mi, s: INTEGER)
			-- Set year, month, day to y, mo, d.
			-- Set hour, minute, second to 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

	make_by_date (d: DATE_DURATION)
			-- Set date to d and time to zero.
		require
			d_exists: d /= void
		ensure
			date_set: date = d
			time_exists: time /= void
			time_set: time.is_equal (time.zero)

	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
		ensure
			date_set: date = d
			time_set: time = t

	make_definite (d, h, m, s: INTEGER)
			-- Set day to d.
			-- Set hour, minute, second to 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

	make_fine (y, mo, d, h, mi: INTEGER; s: DOUBLE)
			-- set year, month, day to y, mo, d.
			-- set hour, minute, second to 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
	
feature -- Access

	date: DATE_DURATION
			-- Date part of the current duration

	date_default_format_string: STRING
			-- Default output format for dates
			-- (from DATE_CONSTANTS)

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

	days_in_i_th_month (i, y: INTEGER): INTEGER
			-- 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

	Days_in_leap_year: INTEGER is 366
			-- Number of days in a leap year
			-- (from DATE_CONSTANTS)

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

	Days_in_week: INTEGER is 7
			-- Number of days in a week
			-- (from DATE_CONSTANTS)

	days_text: ARRAY [STRING]
			-- Short text representation of days
			-- (from DATE_CONSTANTS)

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

	fine_seconds_count: DOUBLE
			-- Total number of seconds of current duration
		require
			has_origin: has_origin_date_time

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

	Hours_in_day: INTEGER is 24
			-- Number of hours in a day
			-- (from TIME_CONSTANTS)

	long_days_text: ARRAY [STRING]
			-- Long text representation of days
			-- (from DATE_CONSTANTS)

	long_months_text: ARRAY [STRING]
			-- Long text representation of months
			-- (from DATE_CONSTANTS)

	Max_weeks_in_year: INTEGER is 53
			-- Maximun number of weeks in a year
			-- (from DATE_CONSTANTS)

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

	Minutes_in_hour: INTEGER is 60
			-- Number of minutes in an hour
			-- (from TIME_CONSTANTS)

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

	Months_in_year: INTEGER is 12
			-- Number of months in year
			-- (from DATE_CONSTANTS)

	months_text: ARRAY [STRING]
			-- Short text representation of months
			-- (from DATE_CONSTANTS)

	origin_date_time: DATE_TIME
			-- Origin date time of duration

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

	seconds_count: INTEGER_64
			-- Total number of seconds of current duration
		require
			has_origin: has_origin_date_time

	Seconds_in_day: INTEGER is 86400
			-- Number of seconds in an hour
			-- (from TIME_CONSTANTS)

	Seconds_in_hour: INTEGER is 3600
			-- Number of seconds in an hour
			-- (from TIME_CONSTANTS)

	Seconds_in_minute: INTEGER is 60
			-- Number of seconds in a minute
			-- (from TIME_CONSTANTS)

	time: TIME_DURATION
			-- Time part of current duration

	time_default_format_string: STRING
			-- Default output format for times
			-- (from TIME_CONSTANTS)

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

	zero: DATE_TIME_DURATION
			-- Neutral element for "+" and "-"
		ensure -- from GROUP_ELEMENT
			result_exists: Result /= void
	
feature -- Comparison

	is_equal (other: like Current): BOOLEAN
			-- Are the current duration an other equal?
		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

	infix "<" (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
		ensure then
			non_definite_result: not (definite and other.definite) implies Result = False

	infix "<=" (other: like Current): BOOLEAN
			-- Is current object less than or equal to other?
			-- (from PART_COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= void

	infix ">" (other: like Current): BOOLEAN
			-- Is current object greater than other?
			-- (from PART_COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= void

	infix ">=" (other: like Current): BOOLEAN
			-- Is current object greater than or equal to other?
			-- (from PART_COMPARABLE)
		require -- from PART_COMPARABLE
			other_exists: other /= void
	
feature -- Status report

	canonical (start_date: DATE_TIME): BOOLEAN
			-- Are the time and date parts of the same sign,
			-- and both canonical?

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

	has_origin_date_time: BOOLEAN
			-- Has an origin_date_time been set?

	is_leap_year (y: INTEGER): BOOLEAN
			-- Is year y a leap year?
			-- (from DATE_CONSTANTS)

	is_negative: BOOLEAN
			-- Is duration negative?
			-- (from DURATION)

	is_positive: BOOLEAN
			-- Is duration positive?

	is_zero: BOOLEAN
			-- Is duration zero?
			-- (from DURATION)
	
feature -- Status setting

	set_origin_date_time (dt: DATE_TIME)
			-- Set origin_date_time to dt.
		ensure
			origin_date_time_set: origin_date_time = dt
			origin_date_set: origin_date_time.date = date.origin_date
	
feature -- Element change

	prefix "+": like Current
			-- Unary plus
			-- (from DURATION)
		ensure -- from GROUP_ELEMENT
			result_exists: Result /= void
			result_definition: Result.is_equal (Current)

	infix "-" (other: like Current): like Current
			-- Difference with other
			-- (from DURATION)
		require -- from GROUP_ELEMENT
			other_exists: other /= void
		ensure -- from GROUP_ELEMENT
			result_exists: Result /= void
	
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
		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))

	to_canonical (start_date: DATE_TIME): like Current
			-- A new duration, equivalent to current one
			-- and canonical for start_date
		ensure
			canonical_set: Result.canonical (start_date)
			duration_not_changed: equal (start_date + Current, start_date + Result)
	
feature -- Basic operations

	day_add (d: INTEGER)
			-- Add d days to the current duration.
		ensure
			result_definition: day = old day + d

	infix "+" (other: like Current): like Current
			-- Sum with other (commutative)
		require -- from GROUP_ELEMENT
			other_exists: other /= void
		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)

	prefix "-": like Current
			-- Unary minus
		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)
	
feature -- Element Change

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

	set_time (t: TIME_DURATION)
			-- Set time to t.
		require
			t_exists: time /= void
		ensure
			time_set: time = t
	
invariant

	date_exists: date /= void
	time_exists: time /= void
	origin_constraint: (origin_date_time = void and date.origin_date = void) or else origin_date_time.date = date.origin_date
	same_signs: (has_origin_date_time and then canonical (origin_date_time)) 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 ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)
		-- from DURATION
	sign_correctness: is_positive xor is_negative xor is_zero
		-- from GROUP_ELEMENT
	neutral_addition: Current.is_equal (Current + zero)
	self_subtraction: zero.is_equal (Current - Current)
		-- from DATE_TIME_MEASUREMENT
	date_exists: date /= void
	time_exists: time /= void

end -- class DATE_TIME_DURATION