anchor.diff:  contains
     ! (T(t+dt) - T(t))/dt = f(s, dt)
     function f (s, dt)
  -!process the right term of \partial T* / \partial t* = (see Recapitulatif des adimensionenemts in report)
  -    use mod_constants
  -    use mod_variables
  +  !process the right term of \partial T* / \partial t* = (see Recapitulatif des adimensionenemts in report)
       implicit none
       
       type(state), intent(in)                    :: s
  
positive.code:   use mod_constants
    use mod_timestep
    use mod_read_parameters
  
    implicit none 
    private
  
negative.code:     states_deriv%T = states%T + dtemp
      
      call compute_variables(states_deriv)
  
      ! Let dT/dt = f0 and d²T/dt² = f1 so T(t+1) = T(t) + dt * f0 * (1 + dt * f1)
      
  