58 lines
1.0 KiB
Plaintext
58 lines
1.0 KiB
Plaintext
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/*
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These objects illustrate a variant of the "diamond problem" using
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a prototype hierarchy.
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In this simple case, the inherited definition which will be used in the
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bottom object is determined by the Logtalk predicate lookup algorithm.
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*/
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% root object, declaring and defining a predicate m/0:
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:- object(a1).
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:- public(m/0).
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m :-
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this(This),
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write('Default definition of method m/0 in object '),
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write(This), nl.
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:- end_object.
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% an object descending from the root object, which redefines predicate m/0:
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:- object(b1,
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extends(a1)).
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m :-
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this(This),
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write('Redefinition of method m/0 in object '),
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write(This), nl.
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:- end_object.
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% another object descending from the root object, which also redefines predicate m/0:
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:- object(c1,
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extends(a1)).
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m :-
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this(This),
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write('Redefinition of method m/0 in object '),
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write(This), nl.
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:- end_object.
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% bottom object, descending from the two previous objects and, as such, inheriting
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% two definitions for the predicate m/0:
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:- object(d1,
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extends(b1, c1)).
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:- end_object.
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