1! { dg-do compile }
2!
3! PR fortran/48821
4!
5! Contributed by Daniel Carrera
6!
7
8contains
9     pure subroutine rk4_vec(t, Y, dY, h)
10         real, intent(inout) :: t, Y(:)
11         real, intent(in) :: h
12         real, dimension(size(Y)) :: k1, k2, k3, k4
13
14         interface
15             pure function dY(t0, y0)
16                 import :: Y
17                 real, intent(in) :: t0, y0(size(Y))
18                 real :: dY(size(y0))
19             end function
20         end interface
21
22         k1 = dY(t, Y)
23         k2 = dY(t + h/2, Y + k1*h/2)
24         k3 = dY(t + h/2, Y + k2*h/2)
25         k4 = dY(t + h  , Y + k3*h)
26
27         Y = Y + (k1 + 2*k2 + 2*k3 + k4) * h/6
28         t = t + h
29     end subroutine
30end
31