Difference between revisions of "Replication"

Revision as of 10:40, 25 August 2006

Work in progress!

We start with some very basic examples, for this we consider all the classes not to be inherited by ANY.

Example set

Basic cases of direct repeated inheritance

The following set of example will base on class B:

class
   B
feature
   f: INTEGER
   g
      do 
         f := f + 1 
      end
end

Three cases of non-conforming repeated inheritance

Lets have look at D1 that repeatedly inherits from B:

class
   D1
inherit {NONE}
   B
      rename f as f_1, g as g_1 end
   B
      rename f as f_2, g as g_2 end
feature
end

And an informal description of the semantics: An object of class D1 contains two physical attributes (f_1 and f_2). A call to feature g_1 results in f_1 being incremented and a call to g_2 increments f_2.

Lets do the same for D2:

class
   D2
inherit {NONE}
   B
      rename g as g_1 end
   B
      rename g as g_2 end
feature
end

An object of class D2 contains one physical attribute (f). A call to either g_1 or g_2 results in f being incremented.

Class D3 should be rejected by the compiler:

class
   D3
inherit {NONE}
   B
      rename f as f_1 end
   B
      rename f as f_2 end
feature
end

Since an object of class D3 would have two physical attributes f_1 and f_2, it is not clear which one g should increment.

Three cases of conforming repeated inheritance

Lets look now at different variants of class DC1. They looks exactly as class D1 except that it inherits conforming from B (twice) and therefore need to solve the conflicts between f_1-f_2 and g_1-g_2 by selecting. Let DC1_f

Even though the following examples contain conforming inheritance, we will start by investigating their semantics in the case where static and dynamic type are equal.