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! { dg-do compile }

!

! PR fortran/48800

!

! Contributed by Daniel Carrera

!

     pure function runge_kutta_step(t, r_, dr, h) result(res)

         real, intent(in) :: t, r_(:), h

         real, dimension(:), allocatable :: k1, k2, k3, k4, res

         integer :: N

         interface

             pure function dr(t, r_)  ! { dg-error "cannot have a deferred shape" }

                 real, intent(in) :: t, r_(:)

                 real :: dr(:)

             end function

         end interface

         N = size(r_)

         allocate(k1(N),k2(N),k3(N),k4(N),res(N))

         k1 = dr(t, r_)

         k2 = dr(t + h/2, r_ + k1*h/2)

         k3 = dr(t + h/2, r_ + k2*h/2)

         k4 = dr(t + h  , r_ + k3*h)

         res = r_ + (k1 + 2*k2 + 2*k3 + k4) * h/6

     end function