core: (merges !621) Add DistanceSquared and LengthSquared methods to …

…Vectors

Complements existing methods to avoid unnecessary square roots in some cases

src/core/model/vector.cc

@@ -88,6 +88,19 @@ Vector2D::GetLength () const
   return std::sqrt (x * x + y * y);
 }
 
+double
+Vector3D::GetLengthSquared () const
+{
+  NS_LOG_FUNCTION (this);
+  return x * x + y * y + z * z;
+}
+double
+Vector2D::GetLengthSquared () const
+{
+  NS_LOG_FUNCTION (this);
+  return x * x + y * y;
+}
+
 double
 CalculateDistance (const Vector3D &a, const Vector3D &b)
 {
@@ -101,6 +114,19 @@ CalculateDistance (const Vector2D &a, const Vector2D &b)
   return (b - a).GetLength ();
 }
 
+double
+CalculateDistanceSquared (const Vector3D &a, const Vector3D &b)
+{
+  NS_LOG_FUNCTION (a << b);
+  return (b - a).GetLengthSquared ();
+}
+double
+CalculateDistanceSquared (const Vector2D &a, const Vector2D &b)
+{
+  NS_LOG_FUNCTION (a << b);
+  return (b - a).GetLengthSquared ();
+}
+
 std::ostream &operator << (std::ostream &os, const Vector3D &vector)
 {
   os << vector.x << ":" << vector.y << ":" << vector.z;

src/core/model/vector.h

@@ -66,6 +66,12 @@ class Vector3D
    */
   double GetLength () const;
 
+  /**
+   * Compute the squared length of the vector.
+   * \returns the vector length squared.
+   */
+  double GetLengthSquared () const;
+
   /**
    * \brief Calculate the Cartesian distance between two points.
    * \param [in] a One point
@@ -74,6 +80,14 @@ class Vector3D
    */
   friend double CalculateDistance (const Vector3D &a, const Vector3D &b);
 
+  /**
+   * \brief Calculate the squared Cartesian distance between two points.
+   * \param [in] a One point
+   * \param [in] b Another point
+   * \returns The distance between \pname{a} and \pname{b}.
+   */
+  friend double CalculateDistanceSquared (const Vector3D &a, const Vector3D &b);
+
   /**
    * Output streamer.
    * Vectors are written as "x:y:z".
@@ -184,6 +198,9 @@ class Vector2D
   /** \copydoc Vector3D::GetLength() */
   double GetLength () const;
 
+  /** \copydoc Vector3D::GetLengthSquared() */
+  double GetLengthSquared () const;
+
   /**
    * \brief Calculate the Cartesian distance between two points.
    * \param [in] a One point
@@ -192,6 +209,14 @@ class Vector2D
    */
   friend double CalculateDistance (const Vector2D &a, const Vector2D &b);
 
+  /**
+   * \brief Calculate the squared Cartesian distance between two points.
+   * \param [in] a One point
+   * \param [in] b Another point
+   * \returns The distance between \pname{a} and \pname{b}.
+   */
+  friend double CalculateDistanceSquared (const Vector2D &a, const Vector2D &b);
+
   /**
    * Output streamer.
    * Vectors are written as "x:y".
@@ -280,6 +305,8 @@ class Vector2D
 
 double CalculateDistance (const Vector3D &a, const Vector3D &b);
 double CalculateDistance (const Vector2D &a, const Vector2D &b);
+double CalculateDistanceSquared (const Vector3D &a, const Vector3D &b);
+double CalculateDistanceSquared (const Vector2D &a, const Vector2D &b);
 std::ostream &operator << (std::ostream &os, const Vector3D &vector);
 std::ostream &operator << (std::ostream &os, const Vector2D &vector);
 std::istream &operator >> (std::istream &is, Vector3D &vector);