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Revision 4601, 1.2 KB
(checked in by pmoura, 7 weeks ago)
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Added svn:mime-type property to source files (set to text/x-logtalk).
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Property svn:mime-type set to
text/x-logtalk
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Property svn:eol-style set to
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Property svn:keywords set to
Author Date Id Revision
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| 1 | /* |
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| 2 | These objects illustrate a variant of the "diamond problem" using |
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| 3 | a prototype hierarchy. |
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| 4 | |
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| 5 | In this simple case, a solution is presented for making two conflicting |
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| 6 | definitions inherited by the bottom object visible through the use of the |
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| 7 | alias/3 predicate directive. |
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| 8 | */ |
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| 9 | |
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| 10 | |
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| 11 | % root object, declaring and defining a predicate m/0: |
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| 12 | |
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| 13 | :- object(a3). |
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| 14 | |
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| 15 | :- public(m/0). |
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| 16 | |
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| 17 | m :- |
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| 18 | this(This), |
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| 19 | write('Default definition of method m/0 in object '), |
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| 20 | write(This), nl. |
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| 21 | |
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| 22 | :- end_object. |
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| 23 | |
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| 24 | |
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| 25 | % an object descending from the root object, which redefines predicate m/0: |
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| 26 | |
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| 27 | :- object(b3, |
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| 28 | extends(a3)). |
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| 29 | |
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| 30 | m :- |
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| 31 | this(This), |
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| 32 | write('Redefinition of method m/0 in object '), |
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| 33 | write(This), nl. |
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| 34 | |
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| 35 | :- end_object. |
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| 36 | |
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| 37 | |
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| 38 | % another object descending from the root object, which also redefines predicate m/0: |
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| 39 | |
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| 40 | :- object(c3, |
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| 41 | extends(a3)). |
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| 42 | |
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| 43 | m :- |
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| 44 | this(This), |
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| 45 | write('Redefinition of method m/0 in object '), |
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| 46 | write(This), nl. |
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| 47 | |
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| 48 | :- end_object. |
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| 49 | |
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| 50 | |
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| 51 | % bottom object, descending from the two previous objects and, as such, inheriting |
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| 52 | % two definitions for the predicate m/0; both inherited definitions are renamed |
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| 53 | % using the alias/3 directive: |
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| 54 | |
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| 55 | :- object(d3, |
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| 56 | extends(b3, c3)). |
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| 57 | |
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| 58 | :- alias(b3, m/0, b3_m/0). |
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| 59 | :- alias(c3, m/0, c3_m/0). |
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| 60 | |
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| 61 | :- end_object. |
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