module swap_module
implicit none

contains
  elemental subroutine swap(x,y)
  integer, intent (inout) :: x, y
  integer :: temp

    temp = x
    x = y
    y = temp
  end subroutine swap
end module swap_module

program ch2006
use swap_module
implicit none
integer, dimension (10) :: a, b
integer :: i

  do i = 1, 10
    a(i) = i
    b(i) = i*i
  end do
  print *, a
  print *, b
  call swap(a,b)
  print *, a
  print *, b
end program ch2006