Elementary classes

A few classes are elementary to TOM. Some of these are defined in the TOM unit (see section unit tom), others are present in the unit built into the compiler, called _builtin_. (Note that it is impossible to refer to this unit directly, as TOM does not allow an identifier to start with an underscore. This is intentional.)

_builtin_.Top

This is the implicit superclass of all defined classes. It contains the definitions of the builtin, statically bound, operators (see section Operators).

_builtin_.Any

This is the implicit subclass of all defined classes. If a method can return any object, it should declare the return type to be Any. In this context, all defined classes are those classes whose location in the inheritance graph is known, i.e. those classes of which the declaration has been read.

tom.State

State is the superclass of all classes with allocatable instances; it is the state introduced by State that allows the dynamic binding and all the other services offered by the runtime to actually function.

tom.All

The instance All defines methods needed for both classes and instances, such as perform :. It is inherited by both the State class and the State instance. It is considered good practice for any behavioural instance which does not inherit anything, to inherit instance (All). Furthermore, if a method accepts all objects as the value for a particular argument, the type of the argument should be All.

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