append.rb in rdf-n3-3.1.2

- old
+ new
@@ -1,13 +1,42 @@
 module RDF::N3::Algebra::List
   ##
-  # Iff the subject is a list of lists and the concatenation of all those lists is the object, then this is true.
+  # Iff the subject is a list of lists and the concatenation of all those lists  is the object, then this is true. The object can be calculated as a function of the subject.
+  #
   # @example
   #     ( (1 2) (3 4) ) list:append (1 2 3 4).
   #
   # The object can be calculated as a function of the subject.
-  class Append < SPARQL::Algebra::Operator::Binary
-    include RDF::Util::Logger
-
+  class Append < RDF::N3::Algebra::ListOperator
     NAME = :listAppend
+    URI = RDF::N3::List.append
+
+    ##
+    # Resolves this operator using the given variable `bindings`.
+    # If the last operand is a variable, it creates a solution for each element in the list.
+    #
+    # @param [RDF::N3::List] list
+    # @return [RDF::Term]
+    # @see RDF::N3::ListOperator#evaluate
+    def resolve(list)
+      flattened = list.to_a.map(&:to_a).flatten
+      # Bind a new list based on the values, whos subject use made up from original list subjects
+      subj = RDF::Node.intern(list.map(&:subject).hash)
+      RDF::N3::List.new(subject: subj, values: flattened)
+    end
+
+    ##
+    # The list argument must be a pair of literals.
+    #
+    # @param [RDF::N3::List] list
+    # @return [Boolean]
+    # @see RDF::N3::ListOperator#validate
+    def validate(list)
+      if super && list.to_a.all? {|li| li.list?}
+        true
+      else
+        log_error(NAME) {"operand is not a list of lists: #{list.to_sxp}"}
+        false
+      end
+    end
   end
 end