| 1 | |
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| 2 | :- object(meta, |
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| 3 | implements(metap)). |
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| 4 | |
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| 5 | |
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| 6 | :- info([ |
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| 7 | version is 1, |
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| 8 | date is 2000/7/24, |
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| 9 | author is 'Paulo Moura', |
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| 10 | comment is 'Useful meta-predicates.']). |
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| 11 | |
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| 12 | |
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| 13 | :- private(apply/3). |
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| 14 | :- metapredicate(apply(*, *, ::)). |
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| 15 | |
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| 16 | :- mode(apply(+callable, +list, -callable), zero_or_more). |
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| 17 | |
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| 18 | :- info(apply/3, [ |
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| 19 | comment is 'Applies a predicate to list of arguments.', |
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| 20 | argnames is ['Predicate', 'Arguments', 'Goal']]). |
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| 21 | |
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| 22 | |
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| 23 | apply(Pred, Args) :- |
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| 24 | apply(Pred, Args, _). |
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| 25 | |
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| 26 | |
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| 27 | apply(Pred, Args, Goal) :- |
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| 28 | (atom(Pred) -> |
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| 29 | Goal =.. [Pred| Args] |
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| 30 | ; |
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| 31 | Pred =.. Old, |
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| 32 | append(Old, Args, New), |
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| 33 | Goal =.. New), |
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| 34 | call(Goal). |
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| 35 | |
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| 36 | |
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| 37 | append([], List, List). |
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| 38 | |
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| 39 | append([Head| Tail], List, [Head| Tail2]) :- |
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| 40 | append(Tail, List, Tail2). |
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| 41 | |
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| 42 | |
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| 43 | callable(Term) :- |
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| 44 | nonvar(Term), |
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| 45 | functor(Term, Functor, _), |
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| 46 | atom(Functor). |
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| 47 | |
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| 48 | |
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| 49 | filter(Pred, In, Out) :- |
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| 50 | filter2(In, Pred, Out). |
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| 51 | |
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| 52 | |
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| 53 | filter2([], _, []). |
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| 54 | |
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| 55 | filter2([Arg| Args], Pred, List) :- |
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| 56 | (apply(Pred, [Arg], _) -> |
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| 57 | List = [Arg| Args2] |
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| 58 | ; |
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| 59 | List = Args2), |
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| 60 | filter2(Args, Pred, Args2). |
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| 61 | |
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| 62 | |
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| 63 | map(Pred, In, Out) :- |
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| 64 | map2(In, Pred, Out). |
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| 65 | |
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| 66 | |
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| 67 | map2([], _, []). |
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| 68 | |
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| 69 | map2([Old| Olds], Pred, [New| News]) :- |
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| 70 | apply(Pred, [Old, New], _), |
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| 71 | map2(Olds, Pred, News). |
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| 72 | |
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| 73 | |
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| 74 | |
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| 75 | succeeds(Pred, List) :- |
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| 76 | succeeds2(List, Pred). |
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| 77 | |
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| 78 | |
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| 79 | succeeds2([], _). |
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| 80 | |
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| 81 | succeeds2([Head| Tail], Pred) :- |
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| 82 | apply(Pred, [Head], _), |
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| 83 | succeeds2(Tail, Pred). |
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| 84 | |
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| 85 | |
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| 86 | :- end_object. |
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