      subroutine  zdscalf(n,da,zx,incx)
c
c     scales a vector by a constant.
c     jack dongarra, 3/11/78.
c     modified 3/93 to return if incx .le. 0.
c     modified 12/3/93, array(1) declarations changed to array(*)
c
      double complex zx(*)
      double precision da
      integer i,incx,ix,n
c
      if( n.le.0 .or. incx.le.0 )return
      if(incx.eq.1)go to 20
c
c        code for increment not equal to 1
c
      ix = 1
      do 10 i = 1,n
        zx(ix) = dcmplx(da,0.0d0)*zx(ix)
        ix = ix + incx
   10 continue
      return
c
c        code for increment equal to 1
c
   20 do 30 i = 1,n
        zx(i) = dcmplx(da,0.0d0)*zx(i)
   30 continue
      return
      end
