anyclass

#anyclass

##Syntax anyclass

##Description There is a predefined class called anyclass, which is the root of the expansion tree. All classes that do not have inherit lists are considered to be expansions of anyclass. The main purpose of anyclass is to allow pointers that can locate objects of any class.

##Example Here is the declaration of a pointer p that can locate an object of any class.

Assuming stack is a class, this creates a stack object and places its location in q and p. The compiler will not allow a call to stack's exported subprograms using p directly, as in:

An assignment from p to q is legal, as in:

This implies a run time check to make sure that p locates an object that is a stack (or a descendant of a stack).

Here is a way to call a subprogram exported from stack using p:

This checks to see that p locates a stack object (or a descendant) before calling the stack operation push.

    var p : pointer to anyclass     % Short form: var p : ^ anyclass
    var q : pointer to stack        % Short form: var q : ^ stack
    new q               % Create a stack object
    p := q              % Legal because p's class
                        % is an ancestor of q's class        p -> push (14)      % ILLEGAL!  anyclass has no operations        q := p  % Checks that p locates a stack object (or descendant)        stack (p) . push (14)   % Checks that p locates a stack object

##Details It is legal to create objects of the class called anyclass, but this is not of much use, because there is nothing you can do with these objects (they have no operations). It is legal to assign these objects to other objects of the same class (anyclass), although this accomplishes nothing.

##See also objectclass.html, which takes a class pointer and produces the class of the object located by the pointer. This is used for testing to determine the class of the object located by a pointer.

See also class.html. See also export.html list, import.html list, inherit.html list, implement.html list and [implement_by.html](implement by) list.