Savesol readsol for P2 FE fields?

Many thanks Frédéric. It works indeed. Here are some line codes for people interested :

fespace Vh(Th, P2);
Vh c, ctest;
// copy the data c into a vector
ctest= c;
// save the P2 FE field
{ofstream ff(“csol.txt”); ff << ctest<< endl;
}
read the P2 FE field
{ifstream gg(“csol.txt”); gg >> ctest3;
}
// plot the read data
plot(ctest3, Th, value=true, wait=true);