subroutine sort(a, n)
c
c -- a variation of bubble sort
c -- figure 6.5
c     
      logical change
      integer n, j, n1
      real a(1)
c
      n1 = n - 1
10    change = .false.
       do 20 j = 1, n1
        if (a(j) .le. a(j+1)) goto 20
         call swap(a(j), a(j+1))
         change = .true.
20     continue
      if (change) goto 10
      return
      end