verbosity=2;
mesh Thxy=triangulate("xyf");
plot(Thxy,wait=1,ps="Thxy.ps");
fespace Vhxy(Thxy,P1);
Vhxy fxy;

{ ifstream file("xyf");
   real xx,yy;
   for(int i=0;i<fxy.n;i++)
   file >> xx >>yy >> fxy[][i]; 
}

plot(fxy,wait=1,ps="xyf.ps");

// new way to bluid a mesh   version 2.23-2
Vhxy xx=x,yy=y;

mesh Th=triangulate(xx[],yy[]);
cout << " region = " <<  triangulate(xx[],yy[])[1].region  <<endl; 
cout << fxy[]'*fxy[] << endl;
plot(Th,wait=1); 
