type t =
  {
    guess             : Guess.t;
    eigenvectors      : Lacaml.D.Mat.t ;
    eigenvalues       : Lacaml.D.Vec.t ;
    nocc              : int;
    energy            : float ;
    nuclear_repulsion : float ;
    kin_energy        : float ;
    eN_energy         : float ;
    coulomb_energy    : float ;
    exchange_energy   : float ;
    iterations        : (float * float * float) array;
  }


let to_string hf_calc =
  let sprintf = Printf.sprintf in
  "
  =====================================================
                     Hartree-Fock                     
  =====================================================
      #       HF energy     Convergence    HOMO-LUMO   
   ---------------------------------------------------" ::
  Array.to_list (Array.mapi (fun i (e, c, g) ->
  sprintf "    %5d   %13.8f   %11.4e   %11.4f  " (i+1) e c g) hf_calc.iterations)

  @ [
"  =====================================================";
     sprintf "%20s energy  %16.10f" "One-electron" (hf_calc.kin_energy +. hf_calc.eN_energy) ;
     sprintf "%20s energy  %16.10f" "Kinetic " hf_calc.kin_energy ;
     sprintf "%20s energy  %16.10f" "Potential" hf_calc.eN_energy ;
"   ---------------------------------------------------";
     sprintf "%20s energy  %16.10f" "Two-electron" (hf_calc.coulomb_energy +. hf_calc.exchange_energy) ;
     sprintf "%20s energy  %16.10f" "Coulomb" hf_calc.coulomb_energy ;
     sprintf "%20s energy  %16.10f" "Exchange" hf_calc.exchange_energy ;
"   ---------------------------------------------------";
     sprintf "%20s energy  %16.10f" "Electronic" (hf_calc.energy -. hf_calc.nuclear_repulsion);
     sprintf "%17s repulsion  %16.10f" "Nuclear" hf_calc.coulomb_energy ;
     sprintf "%20s energy  %16.10f" "Hartree-Fock" hf_calc.energy ;
"  =====================================================" ]
  |> String.concat "\n"