If the expression whose value must be of boolean data type is complex,
it can consist of some subexpressions (see above)
that are put together by logical conjunctions (AND, OR, NOT, .EQUAL TO, NOT EQUAL TO).
If you want to express priority in such an expression, you can use parentheses.
From the conjunctions mentioned below, you can choose either form
(for example, `&&`

or `and`

, etc.).

Every sign of the form `.operator.`

must be
surrounded by a white space.

Logical AND

&&

and

Logical OR

||

or

Logical NOT

!

not

Logical EQUAL TO

==

.eq.

Logical NOT EQUAL TO

!=

<>

.ne.