PROGRAM argumentti
  IMPLICIT NONE
  REAL, DIMENSION(5) :: t1, t2
  EXTERNAL vaihda

  t1 = -1
  t1(2) = 3
  t2 = 2
  CALL suorita(vaihda, t1, t2)
  WRITE (*,*) t1
  WRITE (*,*) t2
CONTAINS
  SUBROUTINE suorita(operaatio, t1, t2)
    IMPLICIT NONE
    EXTERNAL operaatio
    REAL, DIMENSION(:), INTENT(INOUT) :: t1, t2
    INTEGER :: i
    IF (SIZE(t1) /= SIZE(t2)) THEN
      STOP 't1 ja t2 erisuuret!'
    END IF
    DO i = 1, SIZE(t1)
      CALL operaatio(t1(i),t2(i))
    END DO
  END SUBROUTINE suorita
END PROGRAM argumentti

SUBROUTINE vaihda(a,b)
  IMPLICIT NONE
  REAL :: a, b
  REAL :: apu
  apu = a
  a = b
  b = apu
END SUBROUTINE vaihda