subroutine  zdrotf (n,zx,incx,zy,incy,c,s)

c

c     applies a plane rotation, where the cos and sin (c and s) are

c     double precision and the vectors zx and zy are double complex.

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

c

      double complex zx(1),zy(1),ztemp

      double precision c,s

      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

        ztemp = c*zx(ix) + s*zy(iy)

        zy(iy) = c*zy(iy) - s*zx(ix)

        zx(ix) = ztemp

        ix = ix + incx

        iy = iy + incy

   10 continue

      return

c

c       code for both increments equal to 1

c

   20 do 30 i = 1,n

        ztemp = c*zx(i) + s*zy(i)

        zy(i) = c*zy(i) - s*zx(i)

        zx(i) = ztemp

   30 continue

      return

      end