subroutine  cswapf (n,cx,incx,cy,incy)

c

c     interchanges two vectors.

c     jack dongarra, linpack, 3/11/78.

c     modified 12/3/93, array(1) declarations changed to array(*)

c

      complex cx(*),cy(*),ctemp

      integer i,incx,incy,ix,iy,n

c

      if(n.le.0)return

      if(incx.eq.1.and.incy.eq.1)go to 20

c

c       code for unequal increments or equal increments not equal

c         to 1

c

      ix = 1

      iy = 1

      if(incx.lt.0)ix = (-n+1)*incx + 1

      if(incy.lt.0)iy = (-n+1)*incy + 1

      do 10 i = 1,n

        ctemp = cx(ix)

        cx(ix) = cy(iy)

        cy(iy) = ctemp

        ix = ix + incx

        iy = iy + incy

   10 continue

      return

c

c       code for both increments equal to 1

   20 do 30 i = 1,n

        ctemp = cx(i)

        cx(i) = cy(i)

        cy(i) = ctemp

   30 continue

      return

      end