回关于橡皮筋问题——在Lisp中
这是我编的程序中的一个函数，分析分析一下吧(defun select_a_pmx (/ tp val fg ent_pmx pt pt_array n pt1 pt2)
;选择或画出剖切线,返回顶点表pt_array(点1 点2 ...)
(princ "选择(Select)/<第1点>:")
(setq fg 0)
(while fg
(setq tp (car (setq val (grread nil 5))))
(cond
((= 2 tp)
(if (or (= 83 (cadr val)) (= 115 (cadr val)))
(setq fg nil)
)
)
((= 3 tp) (setq fg nil)) ;83、115分别为字母"S"、"s"的ASCII码
)
)
(cond
((= 2 tp) ;键盘按
(while
(null (setq ent_pmx (car (entsel "\n请选择一条剖切线:"))))
)
(setq pt_array (reverse (plvt ent_pmx)))
)
((= 3 tp) ;鼠标
(setq pt (reverse (cdr (reverse (cadr val))))
pt_array (list pt)
)
(setq n1
fg 0
)
(while fg
(setq n (1+ n)
pt1 pt
)
(princ (strcat "\n第" (itoa n) "点:\n"))
(setq pt2 (cadr (grread 0 5)))
(grdraw pt1 pt2 -1)
(while
(and (/= 3 (car (setq val (grread 0 5))))
(/= 11 (car val))
)
(grdraw pt1 pt2 -1)
(setq pt2 (cadr val))
(grdraw pt1 pt2 -1)
)
(if (= 3 (car val))
(progn (setq pt (reverse (cdr (reverse (cadr val))))
pt_array (cons pt pt_array)
)
)
(progn (grdraw pt1 pt2 -1) (setq fg nil))
)
)
(setq pt_array (reverse pt_array))
(command "redraw")
(apply 'command (cons "pline" pt_array))
(command)
(setq ent_pmx (ssname (ssget "L") 0))
)
)
(setq pt_array (list pt_array ent_pmx))
)
主要分析grread函数！ 这样使用GRREAD总觉得不是很合适
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