program q7
  implicit none
  interface
   subroutine display(n)
    integer,dimension(:)::n
   end subroutine
   logical function ok(n)
    integer,dimension(:)::n
   end function
  end interface
  integer,dimension(9)::x
  integer,dimension(6:10)::y
  integer::j,l,u
  do j = 1,9
   x(j) = j
  end do
  l = lbound(x,1)
  u = ubound(x,1)
  call display(x)
  print*,l,u
  do j = 6,10
   y(j) = j+10
  end do
  l = lbound(y,1)
  u = ubound(y,1)
  print*,l,u
  y(7) = -1
  call display(y)
  if (ok(x)) then
   print*,"x is ok"
  else
   print*,"x is not ok"
  end if
  if (ok(y)) then
   print*,"y is ok"
  else
   print*,"y is not ok"
  end if
 end program

 subroutine display(a)
  implicit none
  integer,dimension(:)::a
  integer::i
  do i = 1,size(a)
   print*,"a(",i,") =",a(i)
  end do
 end subroutine 

 logical function ok(a)
! output condition: ok = all entries of a are non-negative
  implicit none
  integer,dimension(:)::a
  logical::ok_so_far
  integer::i
  ok_so_far = .true.
  do i = 1,size(a)
   if (a(i) < 0) ok_so_far = .false.
  end do
  ok = ok_so_far
 end function