Additional logic operators for PostgreSQL

gistfile1.sql

CREATE FUNCTION xor(bool, bool) RETURNS bool AS 'SELECT ($1 AND NOT $2) OR (NOT $1 AND $2);' LANGUAGE 'sql';
CREATE OPERATOR ~| (PROCEDURE='xor', LEFTARG=bool, RIGHTARG=bool);

CREATE FUNCTION condition(bool, bool) RETURNS bool AS 'SELECT CASE WHEN $1 AND NOT $2 THEN false ELSE true END;' LANGUAGE 'sql';
CREATE OPERATOR -> (PROCEDURE='condition', LEFTARG=bool, RIGHTARG=bool);

CREATE FUNCTION bicondition(bool, bool) RETURNS bool AS 'SELECT CASE WHEN ($1 AND $2) OR (NOT $1 and NOT $2) THEN true ELSE false END;' LANGUAGE 'sql';
CREATE OPERATOR <-> (PROCEDURE='bicondition', LEFTARG=bool, RIGHTARG=bool);