anchor.diff:  
         if (flag > 7) then
             write(6,*) 'psi.f : flag > 7'
  -          stop
  +          stop 'error'
         endif
   
   c     # flag = 0      NA
  
positive.code:       if (beta .ne. 0) then
            write(6,'(A,A)') 'psi (psi.f) : Streamfunction only works ',
       &         'for beta == 0'
            stop
        endif
  
  c     # Stream function for rigid body rotation.      
  
negative.code:       if (beta .ne. 0) then
            write(6,'(A,A)') 'psi (psi.f) : Streamfunction only works ',
       &         'for beta == 0'
            stop 'error'
        endif
  
        psi = pi2*revs_per_s*alpha*(pi2*y + alpha*sin(pi2*y))
  