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Operators must be defined on values of specific types. For instance,
+
is defined on numbers, but not on structures. Operators are
often defined on groups of types. For the purposes of Modula-2, the
following definitions hold:
-
Integral types consist of
INTEGER
, CARDINAL
, and
their subranges.
-
Character types consist of
CHAR
and its subranges.
-
Floating-point types consist of
REAL
.
-
Pointer types consist of anything declared as
POINTER TO
type
.
-
Scalar types consist of all of the above.
-
Set types consist of
SET
and BITSET
types.
-
Boolean types consist of
BOOLEAN
.
The following operators are supported, and appear in order of
increasing precedence:
,
-
Function argument or array index separator.
:=
-
Assignment. The value of var
:=
value is
value.
<, >
-
Less than, greater than on integral, floating-point, or enumerated
types.
<=, >=
-
Less than or equal to, greater than or equal to
on integral, floating-point and enumerated types, or set inclusion on
set types. Same precedence as
<
.
=, <>, #
-
Equality and two ways of expressing inequality, valid on scalar types.
Same precedence as
<
. In GDB scripts, only <>
is
available for inequality, since #
conflicts with the script
comment character.
IN
-
Set membership. Defined on set types and the types of their members.
Same precedence as
<
.
OR
-
Boolean disjunction. Defined on boolean types.
AND, &
-
Boolean conjunction. Defined on boolean types.
@
-
The GDB "artificial array" operator (see section Expressions).
+, -
-
Addition and subtraction on integral and floating-point types, or union
and difference on set types.
*
-
Multiplication on integral and floating-point types, or set intersection
on set types.
/
-
Division on floating-point types, or symmetric set difference on set
types. Same precedence as
*
.
DIV, MOD
-
Integer division and remainder. Defined on integral types. Same
precedence as
*
.
-
-
Negative. Defined on
INTEGER
and REAL
data.
^
-
Pointer dereferencing. Defined on pointer types.
NOT
-
Boolean negation. Defined on boolean types. Same precedence as
^
.
.
-
RECORD
field selector. Defined on RECORD
data. Same
precedence as ^
.
[]
-
Array indexing. Defined on
ARRAY
data. Same precedence as ^
.
()
-
Procedure argument list. Defined on
PROCEDURE
objects. Same precedence
as ^
.
::, .
-
GDB and Modula-2 scope operators.
Warning: Sets and their operations are not yet supported, so GDB
treats the use of the operator IN
, or the use of operators
+
, -
, *
, /
, =
, , <>
, #
,
<=
, and >=
on sets as an error.
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