Fixing errors in the matlab implementation of the rational fitter

sources/core/plugins_manager.cpp

@@ -43,6 +43,7 @@ template<typename T> T open_library(const std::string& filename, const char* fun
     else
     {
         std::cerr << "<<ERROR>> unable to load the dynamic library file \"" << filename << "\"" << std::endl;
+		  std::cerr << "          cause: \"" << dlerror() << "\"" << std::endl;
         return NULL;
     }
 #endif

sources/plugins/rational_fitter_matlab/rational_fitter.cpp

@@ -21,9 +21,15 @@ ALTA_DLL_EXPORT fitter* provide_fitter()
 
 rational_fitter_matlab::rational_fitter_matlab() 
 {
+	// Create matlab engine
+	if (!(ep = engOpen(""))) 
+	{
+		std::cerr << "<ERROR>> can't start MATLAB engine" << std::endl ;
+	}
 }
 rational_fitter_matlab::~rational_fitter_matlab() 
 {
+	engClose(ep); 
 }
 
 bool rational_fitter_matlab::fit_data(const data* dat, function* fit, const arguments &args)
@@ -36,14 +42,6 @@ bool rational_fitter_matlab::fit_data(const data* dat, function* fit, const argu
 		return false ;
 	}
 	
-	// Create matlab engine
-	if (!(ep = engOpen(""))) 
-	{
-		std::cerr << "<ERROR>> can't start MATLAB engine" << std::endl ;
-		return false ;
-	}
-	
-
 	// I need to set the dimension of the resulting function to be equal
 	// to the dimension of my fitting problem
 	r->setDimX(d->dimX()) ;
@@ -85,7 +83,6 @@ bool rational_fitter_matlab::fit_data(const data* dat, function* fit, const argu
 		}
 	}
 
-	engClose(ep); 
 	return false ;
 }
 

sources/plugins/rational_fitter_matlab/rational_fitter.h

@@ -28,11 +28,6 @@ class rational_fitter_matlab : public fitter
 		//
 		virtual void set_parameters(const arguments& args) ;
 
-		// Obtain associated data and functions
-		//
-		virtual data*     provide_data() const ;
-		virtual function* provide_function() const ;
-
 	protected: // function
 
 		// Fitting a data object using np elements in the numerator and nq