note description: "References to objects containing a boolean value" library: "Free implementation of ELKS library" status: "See notice at end of class." legal: "See notice at end of class." date: "$Date: 2018-11-14 14:41:36 +0000 (Wed, 14 Nov 2018) $" revision: "$Revision: 102457 $" class BOOLEAN_REF inherit HASHABLE redefine out end create default_create feature -- Access item: BOOLEAN -- Boolean value hash_code: INTEGER_32 -- Hash code value do if item then Result := 1 end end feature {NONE} -- Initialization make_from_reference (v: BOOLEAN_REF) -- Initialize Current with v.item. require v_not_void: v /= Void do set_item (v.item) ensure item_set: item = v.item end feature -- Conversion to_reference: BOOLEAN_REF -- Associated reference of Current do create Result Result.set_item (item) ensure to_reference_not_void: Result /= Void same_item: Result.item = item end to_integer: INTEGER_32 -- 1 if True -- 0 if False do if item then Result := 1 end ensure not_item_implies_zero: not item implies Result = 0 item_implies_one: item implies Result = 1 end feature -- Element change set_item (b: BOOLEAN) -- Make b the item value. do item := b end feature -- Basic operations conjuncted alias "and" (other: like Current): BOOLEAN -- Boolean conjunction with other require other_exists: other /= Void do Result := item and other.item ensure de_morgan: Result = not (not Current or not other) commutative: Result = (other and Current) consistent_with_semi_strict: Result implies (Current and then other) end conjuncted_semistrict alias "and then" (other: like Current): BOOLEAN -- Boolean semi-strict conjunction with other require other_exists: other /= Void do Result := item and then other.item ensure de_morgan: Result = not (not Current or else not other) end implication alias "implies" (other: like Current): BOOLEAN -- Boolean implication of other -- (semi-strict) require other_exists: other /= Void do Result := item implies other.item ensure definition: Result = (not Current or else create {BOOLEAN}.make_from_reference (other)) end negated alias "not": BOOLEAN -- Negation do Result := not item end disjuncted alias "or" (other: like Current): BOOLEAN -- Boolean disjunction with other require other_exists: other /= Void do Result := item or other.item ensure de_morgan: Result = not (not Current and not other) commutative: Result = (other or Current) consistent_with_semi_strict: Result implies (Current or else other) end disjuncted_semistrict alias "or else" (other: like Current): BOOLEAN -- Boolean semi-strict disjunction with other require other_exists: other /= Void do Result := item or else other.item ensure de_morgan: Result = not (not Current and then not other) end disjuncted_exclusive alias "xor" (other: like Current): BOOLEAN -- Boolean exclusive or with other require other_exists: other /= Void do Result := item xor other.item ensure definition: Result = ((Current or other) and not (Current and other)) end feature -- Output out: STRING_8 -- Printable representation of boolean do Result := "False" if item then Result := "True" end end invariant involutive_negation: (not (not Current)).item = item non_contradiction: not ((not Current) and create {BOOLEAN}.make_from_reference (Current)) completeness: (not Current) or create {BOOLEAN}.make_from_reference (Current) note ca_ignore: "CA015", "CA015: double negation" copyright: "Copyright (c) 1984-2018, 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 BOOLEAN_REF
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