SUBROUTINE suorita(operaatio, t1, t2)
  IMPLICIT NONE
  INTERFACE
    SUBROUTINE operaatio(a,b)
      REAL, INTENT(INOUT) :: a, b
    END SUBROUTINE operaatio
  END INTERFACE
  REAL, DIMENSION(:), INTENT(INOUT) :: t1, t2
  INTEGER :: i
  IF (SIZE(t1) /= SIZE(t2)) STOP 't1 ja t2 erisuuret!'
  DO i = 1, SIZE(t1)
    CALL operaatio(t1(i),t2(i))
  END DO
END SUBROUTINE suorita