note
	description: "Durations of time"
	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: time

class 
	TIME_DURATION

create 
	make,
	make_fine,
	make_by_seconds,
	make_by_fine_seconds

feature -- Initialization

	make (h, m, s: INTEGER_32)
			-- Set hour, minute and second to h, m, s respectively.
		do
			hour := h
			minute := m
			fine_second := s.to_double
		ensure
			hour_set: hour = h
			minute_set: minute = m
			second_set: second = s
		end

	make_by_fine_seconds (s: REAL_64)
			-- Set the object by the number of seconds s.
		do
			fine_second := s
			hour := div (second, Seconds_in_hour)
			fine_second := fine_second - (hour * Seconds_in_hour).to_double
			minute := div (second, Seconds_in_minute)
			fine_second := fine_second - (minute * Seconds_in_minute).to_double
		ensure
			minute_large_enough: minute >= 0
			minute_small_enough: minute < Minutes_in_hour
			second_large_enough: second >= 0
			second_small_enough: second < Seconds_in_minute
			fine_seconds_set: dabs (fine_seconds_count - s) <= Tolerance
		end

	make_by_seconds (s: INTEGER_32)
			-- Set the object by the number of seconds s.
		do
			fine_second := s.to_double
			hour := div (s, Seconds_in_hour)
			fine_second := fine_second - (hour * Seconds_in_hour).to_double
			minute := div (second, Seconds_in_minute)
			fine_second := fine_second - (minute * Seconds_in_minute).to_double
		ensure
			seconds_count_set: seconds_count = s
		end

	make_fine (h, m: INTEGER_32; s: REAL_64)
			-- Set hour, minute' and second to h, m and truncated to
			-- integer part of s respectively.
			-- Set fractional_second to the fractional part of s.
		do
			hour := h
			minute := m
			fine_second := s
		ensure
			hour_set: hour = h
			minute_set: minute = m
			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_time_tools: DATE_TIME_TOOLS
			-- Tools for outputting dates and times in different formats
			-- (from TIME_UTILITY)
		once
			create Result
		end

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

	fine_seconds_count: REAL_64
			-- Number of seconds and fractionals of seconds of current duration
		do
			Result := hour * Seconds_in_hour + minute * Seconds_in_minute.to_double + fine_second
		end

	generating_type: TYPE [detachable 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

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

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

	seconds_count: INTEGER_32
			-- Total number of seconds of current duration
		do
			Result := fine_seconds_count.truncated_to_integer
		ensure
			same_count: Result = fine_seconds_count.truncated_to_integer
		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_default_format_string: STRING_8
			-- Default output format for times
			-- (from TIME_CONSTANTS)
		do
			Result := Date_time_tools.Time_default_format_string
		end

	zero: like Current
			-- Neutral element for "+" and "-"
		do
			create Result.make (0, 0, 0)
		ensure -- from GROUP_ELEMENT
			result_exists: Result /= Void
		end
	
feature {NONE} -- Access

	arc_cosine (v: REAL_64): REAL_64
			-- Trigonometric arccosine of radian v
			-- in the range [0, pi].
			-- (from DOUBLE_MATH)
		external
			"C signature (double): double use <math.h>"
		alias
			"acos"
		ensure -- from DOUBLE_MATH
			instance_free: class
		end

	arc_sine (v: REAL_64): REAL_64
			-- Trigonometric arcsine of radian v
			-- in the range [-pi/2, +pi/2].
			-- (from DOUBLE_MATH)
		external
			"C signature (double): double use <math.h>"
		alias
			"asin"
		ensure -- from DOUBLE_MATH
			instance_free: class
		end

	arc_tangent (v: REAL_64): REAL_64
			-- Trigonometric arctangent of radian v
			-- in the range [-pi/2, +pi/2].
			-- (from DOUBLE_MATH)
		external
			"C signature (double): double use <math.h>"
		alias
			"atan"
		ensure -- from DOUBLE_MATH
			instance_free: class
		end

	ceiling (v: REAL_64): REAL_64
			-- Least integral greater than or equal to v.
			-- (from DOUBLE_MATH)
		external
			"C signature (double): double use <math.h>"
		alias
			"ceil"
		ensure -- from DOUBLE_MATH
			instance_free: class
		end

	cosine (v: REAL_64): REAL_64
			-- Trigonometric cosine of radian v approximated
			-- in the range [-pi/4, +pi/4].
			-- (from DOUBLE_MATH)
		external
			"C signature (double): double use <math.h>"
		alias
			"cos"
		ensure -- from DOUBLE_MATH
			instance_free: class
		end

	dabs (v: REAL_64): REAL_64
			-- Absolute of v.
			-- (from DOUBLE_MATH)
		external
			"C signature (double): double use <math.h>"
		alias
			"fabs"
		ensure -- from DOUBLE_MATH
			instance_free: class
		end

	Euler: REAL_64 = 2.7182818284590452353602874713526625
			-- Logarithm base
			-- (from MATH_CONST)

	exp (x: REAL_64): REAL_64
			-- Exponential of v.
			-- (from DOUBLE_MATH)
		external
			"C signature (double): double use <math.h>"
		ensure -- from DOUBLE_MATH
			instance_free: class
		end

	floor (v: REAL_64): REAL_64
			-- Greatest integral less than or equal to v.
			-- (from DOUBLE_MATH)
		external
			"C signature (double): double use <math.h>"
		ensure -- from DOUBLE_MATH
			instance_free: class
		end

	log (v: REAL_64): REAL_64
			-- Natural logarithm of v.
			-- (from DOUBLE_MATH)
		external
			"C signature (double): double use <math.h>"
		ensure -- from DOUBLE_MATH
			instance_free: class
		end

	log10 (v: REAL_64): REAL_64
			-- Base 10 logarithm of v.
			-- (from DOUBLE_MATH)
		external
			"C signature (double): double use <math.h>"
		ensure -- from DOUBLE_MATH
			instance_free: class
		end

	log_2 (v: REAL_64): REAL_64
			-- Base 2 logarithm of v.
			-- (from DOUBLE_MATH)
		do
			Result := log (v) / log ({REAL_64} 2.0)
		ensure -- from DOUBLE_MATH
			instance_free: class
		end

	Pi: REAL_64 = 3.1415926535897932384626433832795029
			-- (from MATH_CONST)

	Pi_2: REAL_64 = 1.5707963267948966192313216916397514
			-- (from MATH_CONST)

	Pi_4: REAL_64 = 0.7853981633974483096156608458198757
			-- (from MATH_CONST)

	sine (v: REAL_64): REAL_64
			-- Trigonometric sine of radian v approximated
			-- in range [-pi/4, +pi/4].
			-- (from DOUBLE_MATH)
		external
			"C signature (double): double use <math.h>"
		alias
			"sin"
		ensure -- from DOUBLE_MATH
			instance_free: class
		end

	sqrt (v: REAL_64): REAL_64
			-- Square root of v.
			-- (from DOUBLE_MATH)
		external
			"C signature (double): double use <math.h>"
		ensure -- from DOUBLE_MATH
			instance_free: class
		end

	Sqrt2: REAL_64 = 1.4142135623730950488016887242096981
			-- Square root of 2
			-- (from MATH_CONST)

	tangent (v: REAL_64): REAL_64
			-- Trigonometric tangent of radian v approximated
			-- in range [-pi/4, +pi/4].
			-- (from DOUBLE_MATH)
		external
			"C signature (double): double use <math.h>"
		alias
			"tan"
		ensure -- from DOUBLE_MATH
			instance_free: class
		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: 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_greater alias ">" (other: 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: 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_equal alias "<=" (other: 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: 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: BOOLEAN
			-- Is duration expressed minimally, i.e.
			--	If duration is positive then
			--		hour positive,
			--		minute and second between 0 and 59,
			--		fractional_second between 0 and 999?
			--	If duration is negative then
			--		hour negative,
			--		minute and second between -59 and 0,
			--		fractional_second between -999 and 0?
		do
			if fine_seconds_count >= 0.to_double then
				Result := fine_second < Seconds_in_minute.to_double and then fine_second >= 0.to_double and then minute < Minutes_in_hour and then minute >= 0
			else
				Result := fine_second > - Seconds_in_minute.to_double and then fine_second <= 0.to_double and then minute > - Minutes_in_hour and then minute <= 0
			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

	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 := hour > 0 or minute > 0 or fine_second > 0.to_double
		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 -- Element change

	identity alias "+": 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: TIME_DURATION): 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_modulo_day: like Current
			-- Duration modulo duration of a day
		do
			create Result.make_by_seconds (mod (fine_seconds_count.floor, Seconds_in_day))
			Result.fine_second_add (fine_seconds_count - fine_seconds_count.floor.to_double)
		ensure
			result_smaller_than_day: Result.seconds_count < Seconds_in_day
			result_positive: Result >= zero
		end

	to_canonical: like Current
			-- A new duration
		do
			if canonical then
				Result := twin
			else
				if fine_seconds_count >= 0.to_double then
					create Result.make_by_fine_seconds (fine_seconds_count)
				else
					create Result.make_by_fine_seconds (- fine_seconds_count)
					Result := - Result
				end
			end
		ensure
			result_canonical: Result.canonical
		end

	to_days: INTEGER_32
			-- Total number of days equivalent to the current duration
		do
			Result := div (fine_seconds_count.floor, Seconds_in_day)
		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: 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: 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: 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: 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: 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: 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 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

	frozen default: detachable 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

	fine_second_add (s: REAL_64)
			-- Add s seconds to the current time.
			-- if s has decimals, fractional_second is modifed.
		do
			fine_second := fine_second + s
		end

	hour_add (h: INTEGER_32)
			-- Add h hours to the current duration.
		do
			hour := hour + h
		ensure
			hour_set: hour = old hour + h
		end

	minute_add (m: INTEGER_32)
			-- Add m minutes to the current duration.
		do
			minute := minute + m
		ensure
			minute_set: minute = old minute + m
		end

	opposite alias "-": like Current
			-- Unary minus
		do
			create Result.make_fine (- hour, - minute, - fine_second)
		ensure -- from GROUP_ELEMENT
			result_exists: Result /= Void
			result_definition: (Result + Current).is_equal (zero)
		end

	plus alias "+" (other: like Current): like Current
			-- Sum with other
		require -- from GROUP_ELEMENT
			other_exists: other /= Void
		do
			create Result.make_fine (hour + other.hour, minute + other.minute, fine_second + other.fine_second)
		ensure -- from GROUP_ELEMENT
			result_exists: Result /= Void
			commutative: Result.is_equal (other + Current)
		end

	second_add (s: INTEGER_32)
			-- Add s seconds to the current duration.
		do
			fine_second := fine_second + s.to_double
		ensure
			second_set: second = old second + s
		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 -- Attributes

	fine_second: REAL_64
			-- Number of fine seconds associated with current object

	fractional_second: REAL_64
		do
			Result := fine_second - second.to_double
		end

	hour: INTEGER_32
			-- Number of hours associated with current object

	minute: INTEGER_32
			-- Number of minutes associated with current object

	second: INTEGER_32
			-- Number of seconds associated with current object.
		do
			Result := fine_second.truncated_to_integer
		end
	
feature -- Comparaison

	is_equal (other: like Current): BOOLEAN
			-- Is the current duration equal to other?
		require -- from ANY
			other_not_void: other /= Void
		do
			Result := fine_seconds_count = other.fine_seconds_count
		ensure -- from ANY
			symmetric: Result implies other ~ Current
			consistent: standard_is_equal (other) implies Result
		end

	is_less alias "<" (other: like Current): BOOLEAN
			-- Is the current duration smaller than other?
		require -- from PART_COMPARABLE
			other_exists: other /= Void
		do
			Result := fine_seconds_count < other.fine_seconds_count
		end
	
feature {NONE} -- Constants

	Tolerance: REAL_64 = 1.0e-06
			-- Tolerance for floating point errors
	
feature -- Element Change

	set_fine_second (s: REAL_64)
			-- Set fine_second to s.
		require -- from TIME_MEASUREMENT
			s_large_enough: s >= 0.to_double
			s_small_enough: s < Seconds_in_minute.to_double
		do
			fine_second := s
		ensure -- from TIME_MEASUREMENT
			fine_second_set: fine_second = s
		end

	set_fractionals (f: REAL_64)
			-- Set fractional_second to f.
			-- f must have the same sign as second.
		require -- from TIME_MEASUREMENT
			f_large_enough: f >= 0.to_double
			f_small_enough: f < 1.to_double
		do
			fine_second := second.to_double + f
		ensure -- from TIME_MEASUREMENT
			second_same: second = old second
		end

	set_hour (h: INTEGER_32)
			-- Set hour to h.
		require -- from TIME_MEASUREMENT
			h_large_enough: h >= 0
			h_small_enough: h < Hours_in_day
		do
			hour := h
		ensure -- from TIME_MEASUREMENT
			hour_set: hour = h
		end

	set_minute (m: INTEGER_32)
			-- Set minute to m.
		require -- from TIME_MEASUREMENT
			m_large_enough: m >= 0
			m_small_enough: m < Minutes_in_hour
		do
			minute := m
		ensure -- from TIME_MEASUREMENT
			minute_set: minute = m
		end

	set_second (s: INTEGER_32)
			-- Set second to s.
			-- fractional_second is cut down to 0.
		require -- from TIME_MEASUREMENT
			s_large_enough: s >= 0
			s_small_enough: s < Seconds_in_minute
		do
			fine_second := s.to_double
		ensure -- from TIME_MEASUREMENT
			second_set: second = s
		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
	fractionals_large_enough: fractional_second > -1.to_double
	fractionals_small_enough: fractional_second < 1.to_double
	fractional_and_second_same_sign: second.to_double * fractional_second >= 0.to_double
	equal_signs: canonical implies (hour >= 0 and minute >= 0 and fine_second >= 0.to_double) or (hour <= 0 and minute <= 0 and fine_second <= 0.to_double)

		-- 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)

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 TIME_DURATION

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