diff --git a/owlps-positioning/TODO b/owlps-positioning/TODO
index 5651c3c..158804e 100644
--- a/owlps-positioning/TODO
+++ b/owlps-positioning/TODO
@@ -1,20 +1,22 @@
 
-- Measurement & Request
-   Actuellement, l'AP associé à chaque Measurement (pointeur) n'est
-   pas initialisé lors de la lecture depuis un InputCSV. Les
-   Measurement sont créés par accès direct dans la table de hachage :
-   measurements[mac_ap].add_ss(ss)
-   C'est donc le constructeur par défaut Measurement() qui est utilisé
-   lors du premier accès.
-
 - InputCSV
    ° Différencier une requête normale d'une requête de calibration, en
    utilisant les champs de direction.
    ° Lire la direction en tant qu'entier plutôt que float ?
 
-- '\n' vs. endl.
-   Utiliser '\n' plutôt que endl lorsque le vidage du tampon n'est pas
-   nécessaire.
+- Commentaires doxygen
+
+- Tests unitaires
+
+- Affichage de debug
+   Garder (generaliser) ? Supprimer ?
+
+- Réorganisation du dépôt ?
+   owlps-positioning/src
+   owlps-positioning/include
+   owlps-positioning/tests/src
+   owlps-positioning/tests/include
+   owlps-positioning/doc (générée par doxygen)
 
 - Measurement
    Vérifier le calcul de moyenne (a priori OK).
@@ -25,14 +27,17 @@
    ° Compositions : devraient être représentées par des attributs
    normaux.
 
-- AccessPoint : attribut float friis_index ?
+- Request
+   Constructeur par recopie, operator==(), etc.
 
-- Mobile : attributs Viterbi ?
-   Cf. l'ancien clientinfo.hh.
+- Area
+   operator=()
 
-- Accesseurs par références ?
-   getref_mon_attribut() (cf. l'ancien clientinfo.hh)
-   −> Accesseur en lecture : retourne une référence constante.
+- AccessPoint
+   Attribut float friis_index ?
+
+- Mobile
+   Attributs Viterbi ? (Cf. l'ancien clientinfo.hh.)
 
 - C++ en action
    Espaces de noms ? 109
diff --git a/owlps-positioning/accesspoint.cc b/owlps-positioning/accesspoint.cc
index 316ced5..0e5ee8b 100644
--- a/owlps-positioning/accesspoint.cc
+++ b/owlps-positioning/accesspoint.cc
@@ -8,7 +8,7 @@ using namespace std ;
 /*** Opérateurs ***/
 
 
-AccessPoint AccessPoint::operator=(const AccessPoint &ap)
+const AccessPoint& AccessPoint::operator=(const AccessPoint &ap)
 {
   if (this == &ap)
     return *this ;
@@ -37,8 +37,8 @@ bool AccessPoint::operator==(const AccessPoint &ap) const
 ostream &operator<<(ostream &os, const AccessPoint &ap)
 {
   os
-      << "Coordinates: " << ap.coordinates << endl
-      << "Frequency: " << ap.frequency << " Hz" << endl
+      << "Coordinates: " << ap.coordinates << '\n'
+      << "Frequency: " << ap.frequency << " Hz" << '\n'
       << (WifiDevice) ap ;
 
   return os ;
diff --git a/owlps-positioning/accesspoint.hh b/owlps-positioning/accesspoint.hh
index 3f525df..e00a177 100644
--- a/owlps-positioning/accesspoint.hh
+++ b/owlps-positioning/accesspoint.hh
@@ -33,13 +33,13 @@ public:
 
   ~AccessPoint() {}
 
-  Point3D get_coordinates(void) const ;
+  const Point3D& get_coordinates(void) const ;
   unsigned int get_frequency(void) const ;
 
   void set_coordinates(Point3D &_coordinates) ;
   void set_frequency(unsigned int &_frequency) ;
 
-  AccessPoint operator=(const AccessPoint &ap) ;
+  const AccessPoint& operator=(const AccessPoint &ap) ;
   bool operator==(const AccessPoint &ap) const ;
   bool operator!=(const AccessPoint &ap) const ;
 
@@ -51,7 +51,7 @@ public:
 /*** Accesseurs lecture ***/
 
 
-inline Point3D AccessPoint::get_coordinates() const
+inline const Point3D& AccessPoint::get_coordinates() const
 {
   return coordinates ;
 }
diff --git a/owlps-positioning/area.hh b/owlps-positioning/area.hh
index 5f5901f..01e1a81 100644
--- a/owlps-positioning/area.hh
+++ b/owlps-positioning/area.hh
@@ -25,9 +25,9 @@ public:
   ~Area() {}
 
   Building* get_building(void) const ;
-  std::string get_name(void) const ;
-  Point3D get_p_min(void) const ;
-  Point3D get_p_max(void) const ;
+  const std::string& get_name(void) const ;
+  const Point3D& get_p_min(void) const ;
+  const Point3D& get_p_max(void) const ;
 
   void set_building(const Building *_building) ;
   void set_name(const std::string &_name) ;
@@ -59,19 +59,19 @@ inline Building* Area::get_building() const
 }
 
 
-inline std::string Area::get_name() const
+inline const std::string& Area::get_name() const
 {
   return name ;
 }
 
 
-inline Point3D Area::get_p_min() const
+inline const Point3D& Area::get_p_min() const
 {
   return p_min ;
 }
 
 
-inline Point3D Area::get_p_max() const
+inline const Point3D& Area::get_p_max() const
 {
   return p_max ;
 }
diff --git a/owlps-positioning/building.cc b/owlps-positioning/building.cc
index eb9f545..586a478 100644
--- a/owlps-positioning/building.cc
+++ b/owlps-positioning/building.cc
@@ -35,13 +35,13 @@ Building::Building(const Building &b)
 Building::~Building()
 {
   // Empty Area list
-  for (vector<Area*>::iterator i = areas.begin() ; i != areas.end() ; i++)
+  for (vector<Area*>::iterator i = areas.begin() ; i != areas.end() ; ++i)
     delete *i ;
   areas.clear() ;
 
   // Empty Waypoint list
   for (vector<Waypoint*>::iterator i = waypoints.begin() ;
-       i != waypoints.end() ; i++)
+       i != waypoints.end() ; ++i)
     {
       // Delete current waypoint only if it is not linked to another building
       if ((*i)->get_buildings().size() <= 1)
@@ -55,7 +55,7 @@ Building::~Building()
 /*** Opérateurs ***/
 
 
-Building Building::operator=(const Building &b)
+const Building& Building::operator=(const Building &b)
 {
   if (this == &b)
     return *this ;
diff --git a/owlps-positioning/building.hh b/owlps-positioning/building.hh
index 916e9f9..6af433a 100644
--- a/owlps-positioning/building.hh
+++ b/owlps-positioning/building.hh
@@ -21,15 +21,15 @@ public :
 
   ~Building(void) ;
 
-  std::string get_name(void) const ;
-  std::vector<Area*> get_areas(void) const ;
-  std::vector<Waypoint*> get_waypoints(void) const ;
+  const std::string& get_name(void) const ;
+  const std::vector<Area*>& get_areas(void) const ;
+  const std::vector<Waypoint*>& get_waypoints(void) const ;
 
   void set_name(const std::string &_name) ;
   void add_area(const Area *a) ;
   void add_waypoint(const Waypoint *wp) ;
 
-  Building operator=(const Building &p) ;
+  const Building& operator=(const Building &p) ;
   bool operator==(const Building &p) const ;
   bool operator!=(const Building &p) const ;
 
@@ -41,19 +41,19 @@ public :
 /*** Accesseurs lecture ***/
 
 
-inline std::string Building::get_name() const
+inline const std::string& Building::get_name() const
 {
   return name ;
 }
 
 
-inline std::vector<Area*> Building::get_areas() const
+inline const std::vector<Area*>& Building::get_areas() const
 {
   return areas ;
 }
 
 
-inline std::vector<Waypoint*> Building::get_waypoints() const
+inline const std::vector<Waypoint*>& Building::get_waypoints() const
 {
   return waypoints ;
 }
diff --git a/owlps-positioning/calibrationmeasurement.cc b/owlps-positioning/calibrationmeasurement.cc
index e176243..1cb2eda 100644
--- a/owlps-positioning/calibrationmeasurement.cc
+++ b/owlps-positioning/calibrationmeasurement.cc
@@ -5,7 +5,7 @@
 /*** Opérateurs ***/
 
 
-CalibrationMeasurement
+const CalibrationMeasurement&
 CalibrationMeasurement::operator=(const CalibrationMeasurement &cm)
 {
   if (this == &cm)
diff --git a/owlps-positioning/calibrationmeasurement.hh b/owlps-positioning/calibrationmeasurement.hh
index ced0ea1..e2bfc61 100644
--- a/owlps-positioning/calibrationmeasurement.hh
+++ b/owlps-positioning/calibrationmeasurement.hh
@@ -26,7 +26,7 @@ public:
 
   void set_reference_point(const ReferencePoint *_rp) ;
 
-  CalibrationMeasurement operator=(const CalibrationMeasurement &cm) ;
+  const CalibrationMeasurement& operator=(const CalibrationMeasurement &cm) ;
   bool operator==(const CalibrationMeasurement &cm) ;
   bool operator!=(const CalibrationMeasurement &cm) ;
 
diff --git a/owlps-positioning/measurement.cc b/owlps-positioning/measurement.cc
index 80021dd..ac6a494 100644
--- a/owlps-positioning/measurement.cc
+++ b/owlps-positioning/measurement.cc
@@ -45,7 +45,7 @@ void Measurement::update_average_ss()
   average_ss = 0 ;
 
   for (vector<int>::iterator i = ss_list.begin() ;
-       i != ss_list.end() ; i++)
+       i != ss_list.end() ; ++i)
     {
       float ss_mwatts =
         pow(10, (float) *i / 10.0) +
@@ -88,7 +88,7 @@ void Measurement::clear()
 /*** Opérateurs ***/
 
 
-Measurement Measurement::operator=(const Measurement &m)
+const Measurement& Measurement::operator=(const Measurement &m)
 {
   if (this == &m)
     return *this ;
@@ -126,7 +126,7 @@ ostream &operator<<(ostream &os, const Measurement &m)
     os << "No values" ;
   else
     for (vector<int>::const_iterator i = m.ss_list.begin() ;
-         i != m.ss_list.end() ; i++)
+         i != m.ss_list.end() ; ++i)
       {
         os << *i ;
         if (i != m.ss_list.end() - 1)
diff --git a/owlps-positioning/measurement.hh b/owlps-positioning/measurement.hh
index af24b0a..8030b58 100644
--- a/owlps-positioning/measurement.hh
+++ b/owlps-positioning/measurement.hh
@@ -24,7 +24,7 @@ public:
   ~Measurement() ;
 
   AccessPoint* get_ap() const ;
-  std::vector<int> get_ss_list() const ;
+  const std::vector<int>& get_ss_list() const ;
   float get_average_ss() const ;
   //float get_ss_square_distance(const float &ss) const ;
 
@@ -33,7 +33,7 @@ public:
   void set_ss_list(const std::vector<int> &_ss_list) ;
   void clear(void) ;
 
-  Measurement operator=(const Measurement &m) ;
+  const Measurement& operator=(const Measurement &m) ;
   bool operator==(const Measurement &m) const ;
   bool operator!=(const Measurement &m) const ;
   operator bool(void) const ;
@@ -52,7 +52,7 @@ inline AccessPoint* Measurement::get_ap() const
 }
 
 
-inline std::vector<int> Measurement::get_ss_list() const
+inline const std::vector<int>& Measurement::get_ss_list() const
 {
   return ss_list ;
 }
diff --git a/owlps-positioning/mobile.cc b/owlps-positioning/mobile.cc
index 25fbc0e..c786bd4 100644
--- a/owlps-positioning/mobile.cc
+++ b/owlps-positioning/mobile.cc
@@ -5,7 +5,7 @@
 /*** Opérateurs ***/
 
 
-Mobile Mobile::operator=(const Mobile &m)
+const Mobile& Mobile::operator=(const Mobile &m)
 {
   if (this == &m)
     return *this ;
diff --git a/owlps-positioning/mobile.hh b/owlps-positioning/mobile.hh
index 8762c3c..9076357 100644
--- a/owlps-positioning/mobile.hh
+++ b/owlps-positioning/mobile.hh
@@ -22,7 +22,7 @@ public:
 
   ~Mobile() {}
 
-  Mobile operator=(const Mobile &m) ;
+  const Mobile& operator=(const Mobile &m) ;
   bool operator==(const Mobile &m) const ;
   bool operator!=(const Mobile &m) const ;
 
diff --git a/owlps-positioning/point3d.cc b/owlps-positioning/point3d.cc
index 6d4983b..085a669 100644
--- a/owlps-positioning/point3d.cc
+++ b/owlps-positioning/point3d.cc
@@ -63,7 +63,7 @@ float Point3D::square_distance(const float &_x,
 /*** Opérateurs ***/
 
 
-Point3D Point3D::operator=(const Point3D &p)
+const Point3D& Point3D::operator=(const Point3D &p)
 {
   if (this == &p)
     return *this ;
diff --git a/owlps-positioning/point3d.hh b/owlps-positioning/point3d.hh
index 4ec4a43..79b5521 100644
--- a/owlps-positioning/point3d.hh
+++ b/owlps-positioning/point3d.hh
@@ -16,7 +16,7 @@ public:
   Point3D(const Point3D &p) ;
   Point3D(const float c[3]) ;
 
-  ~Point3D() {}
+  virtual ~Point3D(void) {}
 
   float get_x(void) const ;
   float get_y(void) const ;
@@ -36,7 +36,7 @@ public:
                  const float &my,
                  const float &mz) const ;
 
-  Point3D operator=(const Point3D &p) ;
+  const Point3D& operator=(const Point3D &p) ;
   bool operator==(const Point3D &p) const ;
   bool operator!=(const Point3D &p) const ;
   bool operator<(const Point3D &p) const ;
diff --git a/owlps-positioning/referencepoint.cc b/owlps-positioning/referencepoint.cc
index 6bfe81d..44fcfe7 100644
--- a/owlps-positioning/referencepoint.cc
+++ b/owlps-positioning/referencepoint.cc
@@ -27,10 +27,10 @@ ReferencePoint::~ReferencePoint()
 //   new_meas.addSsValue(-95);
 
 //   /* Complete measurement vector with unexisting ap (from ref point) */
-//   for (i = 0 ; i < ref_m.size() ; i++)
+//   for (i = 0 ; i < ref_m.size() ; ++i)
 //     {
 //       found = false;
-//       for (j = 0 ; j < test_m.size() && !found ; j++)
+//       for (j = 0 ; j < test_m.size() && !found ; ++j)
 //         if (test_m[j].getMacAddr() == ref_m[i].getMacAddr())
 //           found = true;
 //       if (!found)
@@ -41,10 +41,10 @@ ReferencePoint::~ReferencePoint()
 //     }
 
 //   /* Now, complete ref. point meas. */
-//   for (i = 0 ; i < test_m.size() ; i++)
+//   for (i = 0 ; i < test_m.size() ; ++i)
 //     {
 //       found = false;
-//       for (j = 0 ; j < ref_m.size() && !found ; j++)
+//       for (j = 0 ; j < ref_m.size() && !found ; ++j)
 //         if (test_m[i].getMacAddr() == ref_m[j].getMacAddr())
 //           found = true;
 //       if (!found)
@@ -55,7 +55,7 @@ ReferencePoint::~ReferencePoint()
 //     }
 
 //   /* Now, compute SS distance */
-//   for (i = 0 ; i < test_m.size() ; i++)
+//   for (i = 0 ; i < test_m.size() ; ++i)
 //     {
 //       j = 0;
 //       found = false;
@@ -66,7 +66,7 @@ ReferencePoint::~ReferencePoint()
 //               found = true;
 //               ret += ref_m[j].getSsSquareDistance(test_m[i].getAverage());
 //             }
-//           j++;
+//           ++j;
 //         }
 //     }
 
@@ -83,7 +83,7 @@ ReferencePoint::~ReferencePoint()
 //   CalibrationMeasurement m;
 //   bool inserted = false;
 
-//   for (i = 0 ; i < measurements.size() ; i++)
+//   for (i = 0 ; i < measurements.size() ; ++i)
 //     if (measurements[i].getMacAddr() == mac_a)
 //       {
 //         measurements[i].addSsValue(value);
@@ -110,7 +110,7 @@ ReferencePoint::~ReferencePoint()
 //   for (int j=0; j < length; ++j)
 //     str[j] = tolower(str[j]);
 
-//   for (i = 0 ; i < measurements.size() ; i++)
+//   for (i = 0 ; i < measurements.size() ; ++i)
 //     if (measurements[i].getMacAddr() == str)
 //       {
 //         *p = measurements[i].getAverage();
@@ -125,7 +125,7 @@ ReferencePoint::~ReferencePoint()
 /*** Opérateurs ***/
 
 
-ReferencePoint ReferencePoint::operator=(const ReferencePoint &rp)
+const ReferencePoint& ReferencePoint::operator=(const ReferencePoint &rp)
 {
   if (this == &rp)
     return *this ;
@@ -152,16 +152,16 @@ bool ReferencePoint::operator==(const ReferencePoint &rp) const
 ostream &operator<<(ostream &os, const ReferencePoint &rp)
 {
   // Coordinates
-  os << (Point3D) rp << endl ;
+  os << (Point3D) rp << '\n' ;
 
   // List of measurements
   if (rp.measurements.size() == 0)
-    os << "No measurement." << endl ;
+    os << "No measurement." << '\n' ;
   else
     for (vector<CalibrationMeasurement*>::const_iterator
          i = rp.measurements.begin() ;
-         i != rp.measurements.end() ; i++)
-      os << endl << *i ;
+         i != rp.measurements.end() ; ++i)
+      os << '\n' << *i ;
 
   return os ;
 }
diff --git a/owlps-positioning/referencepoint.hh b/owlps-positioning/referencepoint.hh
index 41b31fd..887d88b 100644
--- a/owlps-positioning/referencepoint.hh
+++ b/owlps-positioning/referencepoint.hh
@@ -22,13 +22,13 @@ public:
 
   ~ReferencePoint() ;
 
-  std::vector<CalibrationMeasurement*> get_measurements() const ;
+  const std::vector<CalibrationMeasurement*>& get_measurements(void) const ;
 
   void add_measurement(const CalibrationMeasurement *cm) ;
   //  float get_ss_square_distance(const vector<CalibrationMeasurement> &m) const ;
   //  bool get_power_for_ap(const string &ap_mac, float *p) const ;
 
-  ReferencePoint operator=(const ReferencePoint &rp) ;
+  const ReferencePoint& operator=(const ReferencePoint &rp) ;
   bool operator==(const ReferencePoint &rp) const ;
   bool operator!=(const ReferencePoint &rp) const ;
 
@@ -40,8 +40,8 @@ public:
 /*** Accesseurs lecture ***/
 
 
-inline
-std::vector<CalibrationMeasurement*> ReferencePoint::get_measurements() const
+inline const
+std::vector<CalibrationMeasurement*>& ReferencePoint::get_measurements() const
 {
   return measurements ;
 }
diff --git a/owlps-positioning/request.cc b/owlps-positioning/request.cc
index cc3d4bf..be520e1 100644
--- a/owlps-positioning/request.cc
+++ b/owlps-positioning/request.cc
@@ -70,7 +70,7 @@ ostream &operator<<(ostream &os, const Request &r)
     os << " No values" ;
   else
     for (unordered_map<string, Measurement>::const_iterator i
-         = r.measurements.begin() ; i != r.measurements.end() ; i++)
+         = r.measurements.begin() ; i != r.measurements.end() ; ++i)
       {
         os << '\n' << i->first << ": " << i->second ;
       }
diff --git a/owlps-positioning/request.hh b/owlps-positioning/request.hh
index 11b6b67..f21d57c 100644
--- a/owlps-positioning/request.hh
+++ b/owlps-positioning/request.hh
@@ -26,7 +26,7 @@ public:
           const std::tr1::unordered_map<std::string, Measurement> &_measurements
           = std::tr1::unordered_map<std::string, Measurement>()) ;
 
-  Mobile* get_mobile() const ;
+  Mobile* get_mobile(void) const ;
 
   void set_mobile(const Mobile *_mobile) ;
   void set_timestamp(const struct timespec &_timestamp) ;
diff --git a/owlps-positioning/waypoint.cc b/owlps-positioning/waypoint.cc
index bab373d..ad0bb37 100644
--- a/owlps-positioning/waypoint.cc
+++ b/owlps-positioning/waypoint.cc
@@ -32,7 +32,7 @@ Waypoint::~Waypoint()
 /*** Opérateurs ***/
 
 
-Waypoint Waypoint::operator=(const Waypoint &wp)
+const Waypoint& Waypoint::operator=(const Waypoint &wp)
 {
   if (this == &wp)
     return *this ;
@@ -63,11 +63,11 @@ ostream &operator<<(ostream &os, const Waypoint &wp)
 
   // List of buildings
   if (wp.buildings.size() == 0)
-    os << endl << "Belongs to no building!" ;
+    os << '\n' << "Belongs to no building!" ;
   else
     for (vector<Building*>::const_iterator i = wp.buildings.begin() ;
-         i != wp.buildings.end() ; i++)
-      os << endl << *i ;
+         i != wp.buildings.end() ; ++i)
+      os << '\n' << *i ;
 
   return os ;
 }
diff --git a/owlps-positioning/waypoint.hh b/owlps-positioning/waypoint.hh
index dcdba23..07ae1ec 100644
--- a/owlps-positioning/waypoint.hh
+++ b/owlps-positioning/waypoint.hh
@@ -24,11 +24,11 @@ public:
   ~Waypoint(void) ;
 
   Building* get_1st_building(void) const ;
-  std::vector<Building*> get_buildings(void) const ;
+  const std::vector<Building*>& get_buildings(void) const ;
 
   void add_building(const Building *_b) ;
 
-  Waypoint operator=(const Waypoint &wp) ;
+  const Waypoint& operator=(const Waypoint &wp) ;
   bool operator==(const Waypoint &wp) const ;
   bool operator!=(const Waypoint &wp) const ;
 
@@ -53,7 +53,7 @@ inline Building* Waypoint::get_1st_building() const
 }
 
 
-inline std::vector<Building*> Waypoint::get_buildings() const
+inline const std::vector<Building*>& Waypoint::get_buildings() const
 {
   return buildings ;
 }
diff --git a/owlps-positioning/wifidevice.cc b/owlps-positioning/wifidevice.cc
index 0143d7e..58bf953 100644
--- a/owlps-positioning/wifidevice.cc
+++ b/owlps-positioning/wifidevice.cc
@@ -32,7 +32,7 @@ WifiDevice::WifiDevice(const WifiDevice &wd)
 /*** Opérateurs ***/
 
 
-WifiDevice WifiDevice::operator=(const WifiDevice &wd)
+const WifiDevice& WifiDevice::operator=(const WifiDevice &wd)
 {
   if (this == &wd)
     return *this ;
@@ -63,9 +63,9 @@ bool WifiDevice::operator==(const WifiDevice &wd) const
 ostream &operator<<(ostream &os, const WifiDevice &wd)
 {
   os
-      << "IP address: " << wd.ip_addr << endl
-      << "MAC address: " << wd.mac_addr << endl
-      << "Antenna gain: " << wd.antenna_gain << "dBi" << endl
+      << "IP address: " << wd.ip_addr << '\n'
+      << "MAC address: " << wd.mac_addr << '\n'
+      << "Antenna gain: " << wd.antenna_gain << "dBi" << '\n'
       << "Output power: " << wd.trx_power << "dBm" ;
 
   return os ;
diff --git a/owlps-positioning/wifidevice.hh b/owlps-positioning/wifidevice.hh
index e8af829..87cab56 100644
--- a/owlps-positioning/wifidevice.hh
+++ b/owlps-positioning/wifidevice.hh
@@ -26,8 +26,8 @@ public:
 
   ~WifiDevice() {}
 
-  std::string get_ip_addr(void) const ;
-  std::string get_mac_addr(void) const ;
+  const std::string& get_ip_addr(void) const ;
+  const std::string& get_mac_addr(void) const ;
   float get_antenna_gain(void) const ;
   float get_trx_power(void) const ;
 
@@ -36,7 +36,7 @@ public:
   void set_antenna_gain(float &_antenna_gain) ;
   void set_trx_power(float &_trx_power) ;
 
-  WifiDevice operator=(const WifiDevice &wd) ;
+  const WifiDevice& operator=(const WifiDevice &wd) ;
   bool operator==(const WifiDevice &wd) const ;
   bool operator!=(const WifiDevice &wl) const ;
 
@@ -48,13 +48,13 @@ public:
 /*** Accesseurs lecture ***/
 
 
-inline std::string WifiDevice::get_ip_addr() const
+inline const std::string& WifiDevice::get_ip_addr() const
 {
   return ip_addr ;
 }
 
 
-inline std::string WifiDevice::get_mac_addr() const
+inline const std::string& WifiDevice::get_mac_addr() const
 {
   return mac_addr ;
 }