johnson@uiucdcsp.CS.UIUC.EDU (09/01/86)
It is actually easy to simulate (in Ada) having a subclass redefine a superclass's method. Each class is simulated by a separate package and the package for a subclass contains a procedure for each method defined in the superclass unless the method was redefined in the subclass. Thus, the Ada code contains no trace of the class hierarchy. The hard part of simulating Smalltalk in Ada is when the class of an object is not known. For example, the collection of subviews of a view contains objects of many classes, each of which can have a separate definition of "display" (actually, displayView). Part of displaying a view is displaying all its subviews. This problem could be solved easily if Ada had procedure valued variables, but it is my understanding that it does not. Please correct me if I am wrong, I am not an Ada expert. Ralph Johnson johnson@p.cs.uiuc.edu uiucdcs!johnson