note
	description: "Packed boolean strings"
	library: "Free implementation of ELKS library"
	status: "See notice at end of class."
	legal: "See notice at end of class."
	names: packed_booleans
	access: index
	representation: array
	size: fixed
	date: "$Date: 2020-02-18 09:43:52 +0000 (Tue, 18 Feb 2020) $"
	revision: "$Revision: 103939 $"

class 
	BOOL_STRING

inherit
	TO_SPECIAL [BOOLEAN]
		export
			{NONE} all
			{BOOL_STRING} area
		redefine
			item,
			at,
			put,
			valid_index,
			copy,
			is_equal
		end

	ANY
		redefine
			copy,
			is_equal
		end

create 
	make

feature -- Initialization

	make (n: INTEGER_32)
			-- Allocate area of n booleans.
		require
			non_negative_size: n >= 0
		do
			make_filled_area (False, n)
		ensure
			correct_allocation: count = n
			all_false: ∀ i: 1 |..| n ¦
					not item (i)
		end
	
feature -- Access

	item alias "[]" (i: INTEGER_32): BOOLEAN assign put
			-- Boolean at i-th position,
			-- beginning at left, 1 origin
			-- Was declared in BOOL_STRING as synonym of at.
		do
			Result := area.item (i - 1)
		end

	at alias "@" (i: INTEGER_32): BOOLEAN assign put
			-- Boolean at i-th position,
			-- beginning at left, 1 origin
			-- Was declared in BOOL_STRING as synonym of item.
		do
			Result := area.item (i - 1)
		end
	
feature -- Comparison

	is_equal (other: like Current): BOOLEAN
			-- Is other attached to an object considered
			-- equal to current object?
		do
			if other = Current then
				Result := True
			else
				Result := area.same_items (other.area, 0, 0, count)
			end
		end
	
feature -- Duplication

	copy (other: like Current)
			-- Update current object using fields of object attached
			-- to other, so as to yield equal objects.
		do
			if other /= Current then
				standard_copy (other)
				set_area (other.area.twin)
			end
		ensure then
			not_shared_if_different: other /= Current implies area /= other.area
			equal_areas: area ~ other.area
		end
	
feature -- Status report

	valid_index (i: INTEGER_32): BOOLEAN
			-- Is i within the bounds of Current?
		do
			Result := (1 <= i) and then (i <= count)
		end
	
feature -- Measurement

	count: INTEGER_32
			-- Number of boolean in the area.
		do
			Result := area.count
		end
	
feature -- Element change

	put (v: like item; i: INTEGER_32)
			-- Put boolean v at i-th position
			-- beginning at left, 1 origin.
		do
			area.put (v, i - 1)
		end

	all_true
			-- Set all booleans to true.
		do
			area.fill_with (True, 0, count - 1)
		ensure
			all_true: ∀ i: 1 |..| count ¦
					item (i)
		end

	all_false
			-- Set all booleans to false.
		do
			area.fill_with (False, 0, count - 1)
		ensure
			all_false: ∀ i: 1 |..| count ¦
					not item (i)
		end
	
feature -- Basic operations

	conjuncted alias "and" (other: like Current): like Current
			-- Logical and of 'Current' and other
		require
			other_not_void: other /= Void
			same_size: other.count = count
		local
			other_area, result_area: like area
			i: INTEGER_32
		do
			create Result.make (count)
			result_area := Result.area
			other_area := other.area
			from
				i := count - 1
			until
				i < 0
			loop
				result_area.put (area.item (i) and other_area.item (i), i)
				i := i - 1
			end
		end

	disjuncted alias "or" (other: like Current): like Current
			-- Logical or of 'Current' and other
		require
			other_not_void: other /= Void
			same_size: other.count = count
		local
			other_area, result_area: like area
			i: INTEGER_32
		do
			create Result.make (count)
			result_area := Result.area
			other_area := other.area
			from
				i := count - 1
			until
				i < 0
			loop
				result_area.put (area.item (i) or other_area.item (i), i)
				i := i - 1
			end
		end

	disjuncted_exclusive alias "xor" (other: like Current): like Current
			-- Logical exclusive or of 'Current' and other
		require
			other_not_void: other /= Void
			same_size: other.count = count
		local
			other_area, result_area: like area
			i: INTEGER_32
		do
			create Result.make (count)
			result_area := Result.area
			other_area := other.area
			from
				i := count - 1
			until
				i < 0
			loop
				result_area.put (area.item (i) xor other_area.item (i), i)
				i := i - 1
			end
		end

	negated alias "not": like Current
			-- Negation of 'Current'
		local
			result_area: like area
			i: INTEGER_32
		do
			create Result.make (count)
			result_area := Result.area
			from
				i := count - 1
			until
				i < 0
			loop
				result_area.put (not area.item (i), i)
				i := i - 1
			end
		end

	right_shifted (n: INTEGER_32): like Current
			-- Right shifted 'Current' set, by n positions
		require
			non_negative_shift: n >= 0
		local
			result_area: like area
			shift_count: INTEGER_32
		do
			create Result.make (count)
			result_area := Result.area
			shift_count := count - n
			if shift_count > 0 then
				result_area.copy_data (area, 0, n, shift_count)
			end
		end

	left_shifted (n: INTEGER_32): like Current
			-- Left shifted 'Current' set, by n positions
		require
			non_negative_shift: n >= 0
		local
			result_area: like area
			shift_count: INTEGER_32
		do
			create Result.make (count)
			result_area := Result.area
			shift_count := count - n
			if shift_count > 0 then
				result_area.copy_data (area, n, 0, shift_count)
			end
		end
	
note
	copyright: "Copyright (c) 1984-2020, 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 BOOL_STRING

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