anchor.diff:          !    L: lua state (bare C pointer).
   
           ! Lua:
  -        !    kinetic_energy{
  -        !           sys = sys_t,
  -        !           nattempts = npop,
  -        !           ncycles = n,
  -        !           beta = beta,
  -        !           fermi_temperature = true/false,
  -        !           rng_seed = seed,
  +        !    kin_args = {
  +        !        nattempts = npop,
  +        !        ncycles = n,
  +        !        beta = beta,
  +        !        fermi_temperature = true/false,
  +        !        rng_seed = seed
           !    }
  +        !
  +        !    kinetic_energy {sys = sys_t, kinetic = kin_args}
   
           use, intrinsic :: iso_c_binding, only: c_ptr, c_int, c_f_pointer
           use const, only: p
  
positive.code: 
      end function lua_ccmc
  
      ! --- table->derived type wrappers ---
  
      subroutine read_qmc_in(lua_state, opts, qmc_in)
  
  
negative.code:         type(c_ptr) :: sys_ptr
          type(sys_t), pointer :: sys
          integer :: opts, err, seed, ncycles, nattempts
          logical :: fermi_temperature, have_seed
          real(p) :: beta
  
          lua_state = flu_copyptr(L)
          call get_sys_t(lua_state, sys)
  
          if (sys%ueg%chem_pot == huge(1.0_p)) call stop_all('lua_kinetic_energy', &
                                                             'chem_pot: chemical potential not supplied.')
  
          opts = aot_table_top(lua_state)
          call read_kinetic_args(lua_state, opts, fermi_temperature, beta, nattempts, ncycles, seed, have_seed)
          call aot_table_close(lua_state, opts)
  
          if (have_seed) then
  