core/segment.{h,cpp}: getMidLength()

This is the N length when there is no D.

algo/core/segment.cpp

@@ -249,6 +249,10 @@ int Segmenter::getRight() const {
   return box_J->start;
 }
 
+int Segmenter::getMidLength() const {
+  return box_J->start - box_V->end - 1;
+}
+
 int Segmenter::getLeftD() const {
   return box_D->start;
 }

algo/core/segment.h

@@ -231,7 +231,14 @@ protected:
    * @return the right position (on forward strand) of the segmentation
    */
   int getRight() const;
+
   
+  /**
+   * @return the number of positions between the left and the right positions
+   */
+  int getMidLength() const;
+
+
   /**
    * @return the left position (on forward strand) of the D segmentation.
    */