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! { dg-do compile }

!

! PR fortran/48821

!

! Contributed by Daniel Carrera

!

contains

     pure subroutine rk4_vec(t, Y, dY, h)

         real, intent(inout) :: t, Y(:)

         real, intent(in) :: h

         real, dimension(size(Y)) :: k1, k2, k3, k4

         interface

             pure function dY(t0, y0)

                 import :: Y

                 real, intent(in) :: t0, y0(size(Y))

                 real :: dY(size(y0))

             end function

         end interface

         k1 = dY(t, Y)

         k2 = dY(t + h/2, Y + k1*h/2)

         k3 = dY(t + h/2, Y + k2*h/2)

         k4 = dY(t + h  , Y + k3*h)

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

         t = t + h

     end subroutine

end