code: def _evaluate(self,R,z,phi=0.,t=0.):
          
          if self._new:
              #if R > 6.: return self._kp(R,z)
              if nu.fabs(z) < 10.**-6.:
                  y= 0.5*self._alpha*R
                  return -nu.pi*R*(special.i0(y)*special.k1(y)-special.i1(y)*special.k0(y))
              kalphamax= 10.
              ks= kalphamax*0.5*(self._glx+1.)
              weights= kalphamax*self._glw
              sqrtp= nu.sqrt(z**2.+(ks+R)**2.)
              sqrtm= nu.sqrt(z**2.+(ks-R)**2.)
              evalInt= nu.arcsin(2.*ks/(sqrtp+sqrtm))*ks*special.k0(self._alpha*ks)
              return -2.*self._alpha*nu.sum(weights*evalInt)
          raise NotImplementedError("Not new=True not implemented for RazorThinExponentialDiskPotential")
docs: NAME:
             _evaluate
          PURPOSE:
             evaluate the potential at (R,z)
          INPUT:
             R - Cylindrical Galactocentric radius
             z - vertical height
             phi - azimuth
             t - time
          OUTPUT:
             potential at (R,z)
          HISTORY:
             2012-12-26 - Written - Bovy (IAS)