note
	description: "Universal constants about 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

class 
	DATE_CONSTANTS

create 
	default_create

feature {NONE} -- Initialization

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

	date_default_format_string: STRING_8
			-- Default output format for dates
		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

	days_in_i_th_month (i, y: INTEGER_32): INTEGER_32
			-- Number of days in the i th month at year y
		require
			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

	Days_in_non_leap_year: INTEGER_32 = 365
			-- Number of days in a non-leap year

	Days_in_week: INTEGER_32 = 7
			-- Number of days in a week

	days_text: ARRAY [STRING_8]
			-- Short text representation of days
		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_CONSTANTS]
			-- 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
		do
			Result := Date_time_tools.Long_days_text
		end

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

	Max_weeks_in_year: INTEGER_32 = 53
			-- Maximun number of weeks in a year

	Months_in_year: INTEGER_32 = 12
			-- Number of months in year

	months_text: ARRAY [STRING_8]
			-- Short text representation of months
		do
			Result := Date_time_tools.Months_text
		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_CONSTANTS): 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_CONSTANTS): BOOLEAN
			-- Is other attached to an object considered
			-- equal to current object?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		ensure -- from ANY
			symmetric: Result implies other ~ Current
			consistent: standard_is_equal (other) implies Result
		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_CONSTANTS): 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

	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

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

	is_leap_year (y: INTEGER_32): BOOLEAN
			-- Is year y a leap year?
		do
			Result := (mod (y, 4) = 0) and ((mod (y, 100) /= 0) or (mod (y, 400) = 0))
		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 -- 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_CONSTANTS)
			-- 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_CONSTANTS)
			-- 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_CONSTANTS
			-- 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_CONSTANTS)
			-- 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_CONSTANTS
			-- 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_CONSTANTS
			-- 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 {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 -- Basic operations

	frozen as_attached: attached DATE_CONSTANTS
		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 DATE_CONSTANTS
			-- 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
	
feature {NONE} -- Implementation

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

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