wifi: add comparison operator for WifiMode

src/wifi/model/wifi-mode.cc

@@ -39,6 +39,19 @@ bool operator == (const WifiMode &a, const WifiMode &b)
 {
   return a.GetUid () == b.GetUid ();
 }
+/**
+ * Compare two WifiModes
+ *
+ * \param a WifiMode
+ * \param b WifiMode
+ *
+ * \return true if a is less than b,
+ *         false otherwise
+ */
+bool operator < (const WifiMode &a, const WifiMode &b)
+{
+  return a.GetUid () < b.GetUid ();
+}
 /**
  * Serialize WifiMode to ostream (human-readable).
  *

src/wifi/model/wifi-mode.h

@@ -237,6 +237,7 @@ private:
 
 /// equality operator
 bool operator == (const WifiMode &a, const WifiMode &b);
+bool operator < (const WifiMode &a, const WifiMode &b);
 std::ostream & operator << (std::ostream & os, const WifiMode &mode);
 std::istream & operator >> (std::istream &is, WifiMode &mode);