72b037275f
git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1288 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
62 lines
1.2 KiB
Plaintext
62 lines
1.2 KiB
Plaintext
/*
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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, a solution is presented for making two conflicting
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definitions inherited by the bottom object visible through the use of the
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alias/3 predicate directive.
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*/
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% root object, declaring and defining a predicate m/0:
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:- object(a3).
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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(b3,
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extends(a3)).
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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(c3,
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extends(a3)).
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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; both inherited definitions are renamed
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% using the alias/3 directive:
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:- object(d3,
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extends(b3, c3)).
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:- alias(b3, m/0, b3_m/0).
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:- alias(c3, m/0, c3_m/0).
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:- end_object.
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