Passing an internal procedure as argument

Question

I want to solve a differential equation lots of times for different parameters. It is more complicated than this, but for the sake of clarity let\'s say the ODE is y\'

Answer 1

You could put this all in a module, and make a a global module variable. Make faux a module procedure. That way, it has access to a.

module ode_module
    double precision::a

    contains

    subroutine f(x,a,ans)
        implicit none
        double precision f,ans,y,tol,c(24),w(9)

        call dverk(1,faux,x,y,1.d0,tol,ind,c,1,w)

    end subroutine 

    subroutine faux(n,xx,yy,yprime)
       implicite none
       integer n
       double precision xx,yy(n),yprime(n)
       yprime(1) = (yy(1)+a)*xx
    end subroutine faux

end module