From: Gary Hallmark <gary.hallmark@oracle.com>

Date: Thu, 16 Mar 2006 09:53:05 -0800

Message-ID: <4419A601.5010105@oracle.com>

To: public-rif-wg@w3.org

Date: Thu, 16 Mar 2006 09:53:05 -0800

Message-ID: <4419A601.5010105@oracle.com>

To: public-rif-wg@w3.org

This is a follow up to last week's email thread where Hassan issued a challenge to write production rules to perform append, presumably restricted to assert actions and the following operations on sequences (or lists): first, rest, cons, isEmpty, and isEqual. First is a terse solution in an ad hoc language: appendArgs([],R) -> appendResult([], R, R) appendArgs([H|T], R) -> appendArgs(T, R) appendArgs([H|T], X), appendResult(T, X) -> appendResult([H|T], X, [H|R]) To perform an append, assert an appendArgs fact, e.g. appendArgs([a b c], [d e]). The result is contained in an appendResult fact, e.g. appendResult([a b c], [d e], [a b c d e]) I have tested this using Oracle's ascii java-like production rule language, which I've attached. /* This is a sample program written in Oracle's java-like rule language (RL). This sample uses Rules to append 2 lists. We use java.util.List, but we use only get(0), isEmpty(), add(0), and subList(1, size()) methods. We define RL functions to look "lispy" that encapsulate the List methods. This doubles as a use-case for user defined functions in RIF, by the way. */ import java.util.*; function cons(Object first, List rest) returns List { List ret = new ArrayList(rest); ret.add(0, first); return ret; } function isEmpty(List list) returns boolean { return list.isEmpty(); } function isEqual(List list1, List list2) returns boolean { return list1.equals(list2); } function first(List list) returns Object { return list.get(0); } function rest(List list) returns List { return list.subList(1, list.size()); } class AppendArgs { List left; List right; } class AppendResult { List left; List right; List result; } rule push { if fact AppendArgs a && !isEmpty(a.left) { assert(new AppendArgs(left: rest(a.left), right: a.right)); } } rule base { if fact AppendArgs a && isEmpty(a.left) { assert (new AppendResult(left: a.left, right: a.right, result: a.right)); } } rule pop { if fact AppendArgs a && !isEmpty(a.left) && fact AppendResult r && isEqual(rest(a.left), r.left) && isEqual(a.right, r.right) { assert(new AppendResult( left: a.left, right: a.right, result: cons(first(a.left), r.result))); } } final List left = Arrays.asList(new String[]{"a", "b", "c"}); final List right = Arrays.asList(new String[]{"d", "e"}); assert(new AppendArgs(left: left, right: right)); rule printResult { if fact AppendResult r && isEqual(r.left, left) && isEqual(r.right, right) { println(r.result); } } run(); //prints: [a, b, c, d, e]Received on Thursday, 16 March 2006 17:53:15 GMT

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