; ono-circle.lsp   11june2009  dmemos 

( define ( circle  xm ym r )
 ( set 'cy r )
 ( set 'cx 0  )
 ( set 'pd ( div (sub 5 (mul r 4)) 4)) 
 ( cpoint xm ym cx cy  ) 
 
 ( while ( < cx cy )
  ( inc cx )
  ( if ( < pd 0 )
     ( set 'pd ( +  pd (* 2 cx ) 1 ))
     ( begin 
        ( dec cy )
        ( set 'pd (+ pd (* 2 ( - cx cy )) 1 ))))
  ( cpoint xm ym cx cy  )
 ))

( define ( cpoint xm ym cx cy )
  ( point (+ xm cx) (+ ym cy ))
  ( point (- xm cx) (+ ym cy ))
  ( point (+ xm cx) (- ym cy ))
  ( point (- xm cx) (- ym cy ))
  ( point (+ xm cy) (+ ym cx ))
  ( point (- xm cy) (+ ym cx ))
  ( point (+ xm cy) (- ym cx ))
  ( point (- xm cy) (- ym cx ))
)