anchor.diff:        real*8 exp1,exp2,exp3,exp4,exp5
         real*8 x1,x2,x,dx1_dp,dx2_dp,dx_dp,dx_dalpha
         real*8 denh1x,numh1x,h1x,dh1x_dx,dh1x_dp,dh1x_dalpha
  -      real*8 gx,dgx_dp
  +      real*8 gx,dgx_dp,dgx_dn,dgx_dagr
         real*8 fxa,dfxa_dalpha
         real*8 Fx,dFx_dp,dFx_dalpha,dFx_dn,dFx_dagr,dFx_dtau
         real*8 ex0,nex0
  
positive.code:       real*8 xe,dfdnx,dfdagrx,dfdtaux
  *     ***** local declarations *****
        real*8 n_13,n_23,n_53,n_83,inv_n,agr2,tauW,tauU
        real*8 p,p_14,dp_dn,dp_dagr
        real*8 z,z2,fz,dz_dn,dz_dagr,dz_dtau
        real*8 alpha,dalpha_dn,dalpha_dagr,dalpha_dtau
  
negative.code:         fdtauc = n*dfca_dtau*(ec0 - ec1)
  
          
  
          xce(i)   = x_parameter*ex     + c_parameter*ec
          fn(i)    = x_parameter*fnx    + c_parameter*fnc
          fdn(i)   = x_parameter*fdnx   + c_parameter*fdnc
  