M2 Operators - Debugging with GDB
Description: Debugging with GDB

Next: Built-In Func/Proc, Up: Modula-2

##### 15.4.8.1 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.