M2 Operators (Debugging with GDB)

15.4.9.1 Operators

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 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: Set expressions 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.