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operator and (operand1, operand2: Boolean) = Result: Boolean;or
operator and (operand1, operand2: integer_type) = Result: integer_type;or
procedure and (var operand1: integer_type; operand2: integer_type);
In GNU Pascal, and
has three built-in meanings:
Boolean
-type expressions.
The result of the operation is of Boolean
type.
By default, and
acts as a short-circuit operator in GPC: If
the first operand is False
, the second operand is not
evaluated because the result is already known to be False
.
You can change this to complete evaluation using the
--no-short-circuit
command-line option or the {$B+}
compiler directive.
operand1
is "and"ed bitwise with
operand2
; the result is stored in operand1
.
The logical and
operator is defined in ISO 7185 Pascal.
According to ISO, you cannot rely on and
being a
short-circuit operator. On the other hand, GPC's default behaviour
does not contradict the ISO standard. (See and_then.)
However, since it seems to be a de-facto standard among ISO Pascal
compilers to evaluate both operands of and
, GPC switches to
--no-short-circuit
mode if one of the language dialect
options selecting ISO Pascal, for instance --extended-pascal
,
is given. Use --short-circuit
to override.
Use of and
as a bitwise operator for integers is a Borland
Pascal extension.
Use of and
as a "procedure" is a GNU Pascal extension.
program AndDemo; var a, b, c: Integer; begin if (a = 0) and (b = 0) then { logical `and' } c := 1 else if (a and b) = 0 then { bitwise `and' } c := 2 else and (c, a) { same as `c := c and a' } end.
Note the difference between the logical and
and the bitwise
and
: When a
is 2 and b
is 4, then a and b
is 0.
Beware: a and b = 0
has nothing to do with
(a = 0) and (b = 0)
!
Since bitwise and
has a higher priority than the =
operator,
parentheses are needed in if (a = 0) and (b = 0)
because otherwise
0 and b
would be calculated first, and the remainder would cause a
parse error.