subroutine flds(r,z,er,ez)
c------------------------------------------------------------------------
c
      include 'fldcom.h'
      include 'ucom.h'
c
      r1=rp
      z1=zp
c-----------------------------------------------------------------------
c*
c     evaluate fields at r1,z1 due to ring of charge at r,z.
      call fldring (r1,z1,r,z,er1,ez1)
      if (rwall.le.0.) go to 10
c---calculate field due to image charge on wall
      if (r.gt.0.9*rwall) go to 5
      call scwall (r,z,erw,ezw)
      er1=er1-erw
      ez1=ez1-ezw
      if (r1.lt.rwall) go to 10
      er1=-erw
      ez1=0.
      go to 10
c---simulate wall by one image ring
    5 continue
      rim=2.*rwall-r
      call fldring (r1,z1,rim,z,erw,ezw)
      er1=er1-erw
      ez1=ez1-ezw
   10 continue
      if (nip.eq.0) go to 50
      erw2=0.
      ezw2=0.
      erw3=0.
      ezw3=0.
      er2=0.
      ez2=0.
      er3=0.
      ez3=0.
           do 40 i=1,nip
           xi=i
           if (rwall.le.0.) go to 25
           if (r.le.0.9*rwall) go to 20
           call fldring (r1,z1,rim,z+xi*pl,erw2,ezw2)
           call fldring (r1,z1,rim,z-xi*pl,erw3,ezw3)
           go to 25
   20      continue
           call scwall (r,z+xi*pl,erw2,ezw2)
           call scwall (r,z-xi*pl,erw3,ezw3)
           if (r1.eq.rwall) go to 30
   25      continue
           call fldring (r1,z1,r,z+xi*pl,er2,ez2)
           call fldring (r1,z1,r,z-xi*pl,er3,ez3)
   30      continue
           er1=er1+er2+er3-erw2-erw3
           ez1=ez1+ez2+ez3-ezw2-ezw3
   40      continue
   50 continue
      er=er1
      ez=ez1
      return
      end
c++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*