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As already said, a new type definition could override the values of
some of the attributes of the supertype. The new values, though, might
still bear some relation with the ones in the supertype. This has led
to the definition of a few different inherintance semantics.
The inher field specify how the new value of the declared
attribute relates to the one in the supertype. It can assume one of
the following values (see 1.5 also):
- redef: The attribute value is completely redefined.
- append: The new value must appended at the end of the one
specified in the supertype. Such an usage is meaningful only for
the Bool and Pred domains.
- inner: The new value is inserted in a corresponding
``placeholder'' (keyword inner) purposedly declared in the
supertype. It can be
used only if the value is a Prolog predicate ( Pred).
Figure 1.5: Inheritance mechanism.
Mon Feb 20 21:59:27 MET 1995