anchor.diff:        if((do_coll .and. part_abs_turn(j).eq.0) .or. (.not.do_coll) ) then
           if(lapeofftlt(ix)) then
             if(lbacktracking) then
  -            call roffpos(xLast(1,j),xLast(2,j),xchk(1),xchk(2),ape(7,ix),ape(8,ix),ape(9,ix))
  +            call roffpos(xLast(1,j),xLast(2,j),xchk(1),xchk(2),ape(9,ix),ape(10,ix),ape(11,ix))
             else
  -            call roffpos(xv1(j),xv2(j),xchk(1),xchk(2),ape(7,ix),ape(8,ix),ape(9,ix))
  +            call roffpos(xv1(j),xv2(j),xchk(1),xchk(2),ape(9,ix),ape(10,ix),ape(11,ix))
             end if
             llostp(j)=checkRE( xchk(1),xchk(2),ape(1,ix),ape(2,ix) ) .or. &
               isnan_mb(xchk(1)).or.isnan_mb(xchk(2))
  
positive.code: 
          if(lapeofftlt(ix)) then
            if(lbacktracking) then
              call roffpos(xLast(1,j),xLast(2,j),xchk(1),xchk(2),ape(7,ix),ape(8,ix),ape(9,ix))
            else
              call roffpos(xv1(j),xv2(j),xchk(1),xchk(2),ape(7,ix),ape(8,ix),ape(9,ix))
            end if
            llostp(j)=checkCR( xchk(1),xchk(2),radius2 ) .or. &
              isnan_mb(xchk(1)).or.isnan_mb(xchk(2))
  
negative.code:   ape(2,ix)=aper
    ape(3,ix)=aper
    ape(4,ix)=aper
    ape(7,ix)=-one
    ape(8,ix)=ape(1,ix)*sqrt(two)
  end subroutine aperture_initCR
  
  
  