Preliminary implementation of stabbing query excluding endpoints

lib/treetop/runtime/interval_skip_list.rb

@@ -12,7 +12,16 @@ def empty?
   end
 
   def containing(n)
-    []
+    containing = []
+    cur_node = head
+    (max_height - 1).downto(0) do |cur_level|
+      while (next_node = cur_node.forward[cur_level]) && next_node.key <= n
+        cur_node = next_node
+        return containing if cur_node.key == n
+      end
+      containing.concat(cur_node.markers[cur_level])
+    end
+    containing
   end
 
   def insert(range, marker)
@@ -54,7 +63,7 @@ def delete(key)
     found_node = find(key, path)
     found_node.remove(path) if found_node.key == key
   end  
-
+  
   def find(key, path)
     cur_node = head
     (max_height - 1).downto(0) do |cur_level|

spec/runtime/interval_skip_list_spec.rb

@@ -44,6 +44,44 @@ def expected_node_heights
     [2, 3, 2, 3, 1]
   end
 
+  def confirm_containing_intervals(range, *markers)
+    (range.begin).upto(range.end) do |i|
+      list.containing(i).should have_markers(*markers)
+    end
+  end
+
+  def contain_marker(marker)
+    ContainMarkers.new(list, [marker])
+  end
+
+  def contain_markers(*markers)
+    ContainMarkers.new(list, markers)
+  end
+
+  class ContainMarkers
+    attr_reader :failure_message
+
+    def initialize(list, expected_markers)
+      @list = list
+      @expected_markers = expected_markers
+    end
+
+    def matches?(target_range)
+      @target_range = target_range
+
+      @target_range.each do |i|
+        markers = @list.containing(i)
+        @expected_markers.each do |expected_marker|
+          unless markers.include?(expected_marker)
+            @failure_message = "Expected #{expected_marker.inspect} to contain #{i}, but it doesn't. #{i} is contained by: #{markers.inspect}."
+            return false
+          end
+        end
+      end
+      true
+    end
+  end
+
   def have_markers(*markers)
     HaveMarkers.new(markers)
   end
@@ -67,7 +105,7 @@ def matches?(target)
     end
 
     def failure_message
-      "expected #{@target.inspect} to include only #{@expected_markers.inspect}"
+      "Expected #{@target.inspect} to include only #{@expected_markers.inspect}"
     end
   end
 
@@ -76,8 +114,12 @@ def failure_message
       list.insert(1..7, :a)
     end
 
-    describe "#containing" do
-      it "returns nothing for 1 or 7" do
+    describe ", #containing" do
+      it "returns only :a from 2 through 6" do
+        (2..6).should contain_marker(:a)
+      end
+
+      it "returns nothing at 1 and 7" do
         list.containing(1).should be_empty
         list.containing(7).should be_empty
       end