Revert "Merge pull request #2500 from linas/anchor-link"

Linking results to the AnchorNode idea now seems like a bad idea,
in retrospect.  The ideas in #2911 seem superior. So trash the
AnchorNode support in the query subsystem.

FWIW, if this kind of thing was wanted, a better solution would
be a new kind of Value, that dequeued from a QueueValue, and
plopped the results onto an AnchorNode. ***This*** is the real
reason for stripping away this code: its not generic enough.

Merge branch 'revert-anchor'

examples/pattern-matcher/README.md

@@ -84,7 +84,6 @@ Basic Examples
 The first five examples provide a basic introduction to basic
 pattern matching.
 
-* `anchor.scm`       -- Obtaining results incrementally.
 * `satisfaction.scm` -- Determining satisfiability of a query.
 * `unify.scm`        -- Basic term unification.
 * `glob.scm`         -- Matching multiple atoms at once.

opencog/atoms/core/ScopeLink.cc

@@ -360,10 +360,6 @@ ContentHash ScopeLink::scope_hash(const FreeVariables::IndexMap& index) const
 	// As to not mix together VariableList and VariableSet
 	fnv1a_hash(hsh, _variables._ordered);
 
-	// If there's an AnchorNode, hash that too.
-	if (_variables._anchor)
-		fnv1a_hash(hsh, _variables._anchor->get_hash());
-
 	Arity vardecl_offset = _vardecl != Handle::UNDEFINED;
 	Arity n_scoped_terms = get_arity() - vardecl_offset;
 	fnv1a_hash(hsh, n_scoped_terms);

opencog/atoms/core/Variables.cc

@@ -139,10 +139,6 @@ void Variables::validate_vardecl(const Handle& hdecls)
 		// variables inference is aborted for now.
 		return;
 	}
-	else if (ANCHOR_NODE == tdecls)
-	{
-		_anchor = hdecls;
-	}
 	else
 	{
 		throw InvalidParamException(TRACE_INFO,
@@ -164,10 +160,6 @@ void Variables::validate_vardecl(const HandleSeq& oset)
 		{
 			unpack_vartype(h);
 		}
-		else if (ANCHOR_NODE == t)
-		{
-			_anchor = h;
-		}
 		else
 		{
 			throw InvalidParamException(TRACE_INFO,
@@ -686,7 +678,6 @@ Handle Variables::get_vardecl() const
 
 	if (_ordered)
 		return HandleCast(createVariableList(std::move(vardecls)));
-
 	return HandleCast(createVariableSet(std::move(vardecls)));
 }
 

opencog/atoms/core/Variables.h

@@ -68,8 +68,8 @@ struct Variables : public FreeVariables
 	/// _typemap holds back-ponters to TypedVariableLinkPtrs
 	VariableTypeMap _typemap;
 
-	/// Anchor, if present, else undefined.
-	Handle _anchor;
+	// See VariableList.cc for comments
+	void get_vartype(const Handle&);
 
 	// Validate the variable decls
 	void validate_vardecl(const Handle&);

opencog/atoms/pattern/BindLink.cc

@@ -69,16 +69,6 @@ ValuePtr BindLink::execute(AtomSpace* as, bool silent)
 	OC_ASSERT(qv->is_closed(), "Unexpected queue state!");
 	HandleSeq rslt(qv->to_handle_seq());
 
-	// If there is an anchor, then attach results to the anchor.
-	// Otherwise, create a SetLink and return that.
-	if (_variables._anchor and as)
-	{
-		for (const Handle& h: rslt)
-			as->add_link(MEMBER_LINK, h, _variables._anchor);
-
-		return _variables._anchor;
-	}
-
 	// The result_set contains a list of the grounded expressions.
 	// (The order of the list has no significance, so it's really a set.)
 	// Put the set into a SetLink, cache it, and return that.

opencog/atoms/pattern/DualLink.cc

@@ -79,21 +79,6 @@ ValuePtr DualLink::execute(AtomSpace* as, bool silent)
 	if (nullptr == as) as = _atom_space;
 	Recognizer reco(as);
 	reco.satisfy(PatternLinkCast(get_handle()));
-
-	// If there is an anchor, then attach results to the anchor.
-	// Otherwise, create a SetLink and return that.
-	// XXX FIXME ... at this time, there is no documented way of
-	// squeezing an AnchorLink into a DualLink.  So the below
-	// if-statement is never taken. Some additional design work
-	// is needed.
-	if (_variables._anchor and as)
-	{
-		for (const Handle& h : reco._rules)
-			as->add_link(MEMBER_LINK, h, _variables._anchor);
-
-		return _variables._anchor;
-	}
-
 	return as->add_atom(createUnorderedLink(reco._rules, SET_LINK));
 }
 

opencog/atoms/pattern/GetLink.cc

@@ -53,16 +53,6 @@ ValuePtr GetLink::execute(AtomSpace* as, bool silent)
 	OC_ASSERT(qv->is_closed(), "Unexpected queue state!");
 	HandleSet hs(qv->to_handle_set());
 
-	// If there is an anchor, then attach results to the anchor.
-	// Otherwise, create a SetLink and return that.
-	if (_variables._anchor and as)
-	{
-		for (const Handle& h : hs)
-			as->add_link(MEMBER_LINK, h, _variables._anchor);
-
-		return _variables._anchor;
-	}
-
 	// Create the satisfying set, and cache it.
 	Handle satset(createUnorderedLink(std::move(hs), SET_LINK));
 

opencog/atoms/pattern/SatisfactionLink.cc

@@ -52,12 +52,6 @@ TruthValuePtr SatisfactionLink::evaluate(AtomSpace* as, bool silent)
 	Satisfier sater(as);
 	sater.satisfy(PatternLinkCast(get_handle()));
 
-	// If there is an anchor, then attach results to the anchor.
-	if (_variables._anchor and as)
-	{
-		as->add_link(MEMBER_LINK, sater._ground, _variables._anchor);
-	}
-
 	return sater._result;
 }
 

tests/query/CMakeLists.txt

@@ -59,7 +59,6 @@ ADD_CXXTEST(RecognizerUTest)
 ADD_CXXTEST(ArcanaUTest)
 ADD_CXXTEST(SubstitutionUTest)
 ADD_CXXTEST(GetLinkUTest)
-ADD_CXXTEST(AnchorUTest)
 ADD_CXXTEST(NotLinkUTest)
 ADD_CXXTEST(GetStateUTest)
 ADD_CXXTEST(ClassicalBooleanUTest)
@@ -150,7 +149,6 @@ TARGET_LINK_LIBRARIES(SparseUTest
 )
 
 # -------------------------------------------------------------
-
 # Run only the tests in this subdirectory
 ADD_CUSTOM_TARGET (qtest
 	DEPENDS tests