PlaceHolder type is declared in Global.hpp

latan/Global.hpp

@@ -108,6 +108,11 @@ using ConstMap = Eigen::Map<const Derived>;
 // Index type //////////////////////////////////////////////////////////////////
 typedef DMatBase::Index Index;
 
+// Placeholder type ////////////////////////////////////////////////////////////
+struct PlaceHolder {};
+
+extern PlaceHolder _;
+
 // Type utilities //////////////////////////////////////////////////////////////
 // pointer type test
 template <typename Derived, typename Base>

latan/XYStatData.hpp

@@ -55,11 +55,7 @@ private:
 /******************************************************************************
  *                    object for X vs. Y statistical data                     *
  ******************************************************************************/
-struct PlaceHolder {};
+class XYStatData: public FitInterface
-
-extern PlaceHolder _;
-
-class XYStatData
 {
 public:
     enum