Fix how unknown word uses links

link-grammar/dict-atomese/local-as.h

@@ -63,6 +63,7 @@ Exp* make_sect_exprs(Dictionary dict, const Handle& germ);
 Exp* make_pair_exprs(Dictionary dict, const Handle& germ);
 Exp* make_cart_pairs(Dictionary dict, const Handle& germ, int arity, bool any);
 Exp* make_any_exprs(Dictionary dict);
+Exp* make_cart_any(Dictionary dict, int arity);
 
 void or_enchain(Dictionary, Exp* &orhead, Exp*);
 void and_enchain_left(Dictionary, Exp* &orhead, Exp* &ortail, Exp*);

link-grammar/dict-atomese/lookup-atomese.cc

@@ -427,7 +427,10 @@ Dict_node * as_lookup_list(Dictionary dict, const char *s)
 
 	if (local->enable_unknown_word and 0 == strcmp(s, "<UNKNOWN-WORD>"))
 	{
-		Exp* exp = make_any_exprs(dict);
+		// XXX Note the hard-coded 6. I do not understand why 2 is not
+		// enough. See issue #1351 for a discussion.
+		// https://github.com/opencog/link-grammar/issues/1351
+		Exp* exp = make_cart_any(dict, 6);
 		return make_dn(dict, exp, ssc);
 	}
 

link-grammar/dict-atomese/word-pairs.cc

@@ -241,4 +241,37 @@ Exp* make_any_exprs(Dictionary dict)
 	return any;
 }
 
+/// Much like make_part_pairs, except that this duplicates the
+/// ANY connector. It creates the expression
+/// {@ANY- or @ANY+} and {@ANY- or @ANY+} and ... and {@ANY- or @ANY+}
+/// This cartesian allows multiple connectors to participate in loops.
+/// However, the behavior is ... sruprising. See
+///    https://github.com/opencog/link-grammar/issues/1351
+/// for a discussion of what this is all about.
+Exp* make_cart_any(Dictionary dict, int arity)
+{
+	if (0 >= arity) return nullptr;
+
+	Exp* andhead = nullptr;
+	Exp* andtail = nullptr;
+
+	Exp* any = make_any_exprs(dict);
+
+	Exp* optex = make_optional_node(dict->Exp_pool, any);
+
+	// If its 1-dimensional, we are done.
+	if (1 == arity) return optex;
+
+	and_enchain_right(dict, andhead, andtail, optex);
+
+	for (int i=1; i< arity; i++)
+	{
+		Exp* opt = make_optional_node(dict->Exp_pool, any);
+		and_enchain_right(dict, andhead, andtail, opt);
+	}
+
+	return andhead;
+}
+
+// ===============================================================
 #endif // HAVE_ATOMESE