anchor.diff:  
       elemental real(fp) function E(cosg)
         real(fp), intent(in) :: cosg
  -      E = E0(cosg)
  +      E = E0(cosg) * (1 - par % beta) + E4(cosg) * (par % beta)
       end function
   
     end subroutine
  
positive.code: 
      elemental real(fp) function g(costh)
        real(fp), intent(in) :: costh
        g = 1
      end function
  
      elemental real(fp) function E0(cosg) result(E)
  
negative.code:   implicit none
  
    type modelpar
      real(fp) :: skybg  = 1.5d-10
      real(fp) :: alpha  = 0.4
      real(fp) :: relabs = 0.5
      real(fp) :: hscale = 5000.0
      real(fp) :: beta   = 0.2
    end type
  
  contains
  