Design patterns and Fortran 2003

interface ! ! Subroutine for storing the initial values ! subroutine initial( solver, initial_data ) type(ode_solver) :: solver real, dimension(:) :: initial_data end subroutine initial ! ! Function to compute the derivative ! function eval_deriv( x, t ) real, dimension(:) :: x real, dimension(size(x)) :: eval_deriv ! Derivative is array of ! same size as x real :: t end function eval_deriv ! ! Interface function to hide the internal workings ! function next(solver, time, time_step) type(ode_solver) :: solver real :: time real :: time_step real, dimension(size(ode_solver%state)) :: next_step end function next_step ! ! Function to actually compute the new values ! function solve_step(solver, time, time_step) type(ode_solver) :: solver real :: time real :: time_step real, dimension(size(ode_solver%state)) :: next_step 9 ACM Fortran Forum, December 2008, 27, 3 end function next_step end interface ! ! Declaration of the functions ! procedure(initial) :: initial_values procedure(next) :: next_step procedure(solve_step) :: solve_euler procedure(solve_step) :: solve_heun procedure(solve_step) :: solve_runge_kutta procedure(solve_step) :: ... ! ! Definition of the specific methods for ! solving the ODE ! type(ode_method), dimension(10) :: solvers = & (/ ode_method(solve_euler), ode_method(solve_heun), & ode_method(solve_runge_kutta), ... /)