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@@ -12,6 +12,12 @@ class IntervalSkipList
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     head.forward[0].nil?
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   end
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+  def expire(range, length_change)
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+    containing(range.first).each do |marker|
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+      delete(marker)
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+    end
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+  end
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+
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   def containing(n)
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     containing = []
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     cur_node = head

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@@ -2,7 +2,113 @@ require File.expand_path("#{File.dirname(__FILE__)}/../../spec_helper")
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 require File.expand_path("#{File.dirname(__FILE__)}/spec_helper")
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 describe IntervalSkipList do
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-  describe "#expire_range" do
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+  it_should_behave_like "the palindromic fixture"
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+  describe "when 7..7 is expired with a length change of 0" do
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+    before do
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+      list.expire(7..7, 0)
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+    end
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+
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+    describe " #nodes" do
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+      attr_reader :nodes, :node
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+
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+      before do
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+        @nodes = list.nodes
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+      end
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+
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+      it "has a size of 4" do
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+        nodes.size.should == 4
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+      end
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+
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+      describe "[0]" do
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+        before do
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+          @node = nodes[0]
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+        end
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+
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+        it "has a key of 1 and a height of 3" do
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+          node.key.should == 1
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+          node.height.should == 3
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+        end
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+
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+        it "has no forward markers at level 0" do
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+          node.forward_markers[0].should be_empty
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+        end
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+
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+        it "has :a and :b as its only forward markers on level 1" do
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+          node.forward_markers[1].should have_markers(:a, :b)
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+        end
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+
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+        it "has :c as its only forward marker on level 2" do
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+          node.forward_markers[2].should have_markers(:c)
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+        end
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+
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+        it "has no markers" do
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+          node.markers.should be_empty
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+        end
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+      end
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+
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+      describe "[1]" do
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+        before do
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+          @node = nodes[1]
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+        end
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+
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+        it "has a key of 3 and a height of 2" do
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+          node.key.should == 3
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+          node.height.should == 2
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+        end
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+
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+        it "has :b as its only forward marker on level 0" do
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+          node.forward_markers[0].should have_markers(:b)
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+        end
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+
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+        it "has no forward markers on level 1" do
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+          node.forward_markers[1].should be_empty
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+        end
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+
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+        it "has :a and :b as its only markers" do
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+          node.markers.should have_markers(:a, :b)
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+        end
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+      end
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+
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+      describe "[2]" do
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+        before do
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+          @node = nodes[2]
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+        end
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+
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+        it "has a key of 5 and a height of 1" do
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+          node.key.should == 5
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+          node.height.should == 1
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+        end
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+
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+        it "has no forward markers on level 0" do
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+          node.forward_markers[0].should be_empty
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+        end
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+
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+        it "has :b as its only marker" do
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+          node.markers.should have_markers(:b)
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+        end
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+      end
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+
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+      describe "[3]" do
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+        before do
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+          @node = nodes[3]
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+        end
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+
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+        it "has a key of 7 and a height of 3" do
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+          node.key.should == 7
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+          node.height.should == 3
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+        end
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+
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+        it "has no forward markers at any level" do
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+          node.forward_markers[0].should be_empty
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+          node.forward_markers[1].should be_empty
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+          node.forward_markers[2].should be_empty
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+        end
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+
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+        it "has :c as its only marker" do
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+          node.markers.should have_markers(:c)
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+        end
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+      end
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+    end
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   end
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 end
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