In EDL, dot access refers to expressions of the form
a.b, and can be used in a number of ways.
Typically when dot-based access is brought up, it is referring to the method inherited from GML, in which
a is an integer referencing an instance ID or object index, and
b is a local variable. This expression will look up an object with either an ID or Object index of
a, then access
b from within its scope. This is useful for objects and instances accessing a local variable of another object or instance, either to read or change it.
EDL also inherits the dot operator from C++. It can therefore also be used to access explicit fields in structures and classes, whether the base
a is itself an instance of that structure, or a pointer to such an instance.
Finally, functions can also be accessed in this way, which is not a feature of GML or C++ (except as class members). The most obvious example of this is class members, such as
a is again an instance of a structure/class, and
func is a member function of that class. Of course, this is only useful if said structure/class already defined such a function.
The more interesting implication is instance-scoped functions, for example,
a.instance_destroy() would function exactly the same as
with (a) instance_destroy(). Note that instance-scoped functions are not implemented at this time, but are planned for the near future. In the meantime, simply use
with as a workaround. Member functions and field access, however, are implemented.