Logical_Operators

 A logical operator evaluates one or more Boolean expressions and
 returns a Boolean value.

 Logical Operators:

    operator    |  example       |    result
    -------------------------------------------------
      AND           A AND B         TRUE if both A and B are TRUE

      OR            A OR B          TRUE if either A or B is TRUE, 
                                    or if both are TRUE

      NOT           NOT A           TRUE if A is FALSE, and 
                                    FALSE if A is TRUE

      AND_THEN      A AND_THEN B    TRUE if both A and B are TRUE
                                    (forces left-to-right evaluation
                                     order with short-circuiting)

      OR_ELSE       A OR_ELSE B     TRUE if either A or B is TRUE,
                                    or if both are TRUE
                                    (forces left-to-right evaluation
                                     order with short-circuiting)