### or

#### Synopsis

operator or (operand1, operand2: Boolean) = Result: Boolean;

or

operator or (operand1, operand2: `integer_type`) = Result: `integer_type`;

or

procedure or (var operand1: `integer_type`; operand2: `integer_type`);

#### Description

In GNU Pascal, or has three built-in meanings:

- Logical “or” between two Boolean-type expressions.
The result of the operation is of Boolean type.
By default, or acts as a short-circuit operator in GPC: If
the first operand is True, the second operand is not
evaluated because the result is already known to be True. You
can change this to complete evaluation using the
--no-short-circuit command-line option or the {$B+}
compiler directive.

- Bitwise “or” between two integer-type expressions.
The result is of the common integer type of both expressions.
- Use as a “procedure”: operand1 is “or”ed bitwise with
operand2; the result is stored in operand1.

#### Conforming to

The logical or operator is defined in ISO 7185 Pascal.

According to ISO, you cannot rely on or being a short-circuit
operator. On the other hand, GPC's default behaviour does *not*
contradict the ISO standard. (See or_else.) However, since it
seems to be a de-facto standard among ISO Pascal compilers to
evaluate both operands of or, 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 or as a bitwise operator for integers is a Borland
Pascal extension.

Use of or as a “procedure” is a GNU Pascal extension.

#### Example

program OrDemo;
var
a, b, c: Integer;
begin
if (a = 0) or (b = 0) then { logical `or' }
c := 1
else if (a or b) = 0 then { bitwise `or' }
c := 2
else
or (c, a) { same as `c := c or a' }
end.

Note the difference between the logical or and the bitwise
or: When a is 2 and b is 4, then a or b
is 6. **Beware:** a or b = 0 happens to mean the same as
(a = 0) and (b = 0). (Note the and!)

Since bitwise or has a higher priority than the =
operator, parentheses are needed in if (a = 0) or (b = 0)
because otherwise 0 or b would be calculated first, and the
remainder would cause a parse error.

#### See also

Keywords, and, xor, Operators.