(defun fplot (expr steps xpi ypi / xn yn zn tlist plist _plot)
  (defun _plot (l / i j)
    (setq i 0)
    (command "_3dmesh" (length l) (length (car l)))
    (repeat (length l)
      (setq j 0)
      (repeat (length (car l))
	(command (nth j (nth i l)))
	(setq j (1+ j))
      )
      (setq i (1+ i))
    )
  )				       ; **********************
  (setvar "blipmode" 0)
  (setvar "cmdecho" 0)
  (setq plist nil)
  (setq xn 0.0
	yn 0.0
  )
  (repeat (* xpi steps)
    (setq tlist nil)
    (setq yn 0.0)
    (repeat (* ypi steps)
      (setq zn ((eval expr) xn
	     yn
	    )
      )
      (setq tlist (append
		    tlist
		    (list (list xn yn zn))
		  )
      )
      (setq yn (+ yn (/ pi steps)))
    )
    (setq plist (append
		  plist
		  (list tlist)
		)
    )
    (setq xn (+ xn (/ pi steps)))
  )
  (_plot plist)
)