请帮忙解决“零长度线“的问题！！！

sucy

我用lisp写了一个pline画折线的程序，可为什么有时好使有时不好使，总出现“零长度线”？代码如下： (defun C:jkx(/ jl nzl nzd pt1 pt2 dis pt3 pt4 pt5 pt6 pt7 pt8)
(setvar "CMDECHO" 0)
(setq jl (getreal "\n长度1<200>:"))
(if (= jl nil) (setq jl 200))
(princ jl)
(setq nzl (getreal "\n长度2<3000>:"))
(if (= nzl nil) (setq nzl 3000))
(setq nzd (getreal "\n长度3<300>:"))
(if (= nzd nil) (setq nzd 300))
(setq pt1 (getpoint "\n第一点:"))
(setq pt2 (getpoint pt1 "\n第二点:"))
(setq ang (angle pt1 pt2))
(setq dis (distance pt1 pt2)) (setq pt3 (polar pt1 ang jl))
(setq pt4 (polar pt3 (+ ang 1.570796327) (/ nzd 2)))
(setq pt5 (polar pt4 ang nzl))
(setq pt6 (polar pt5 (- ang 1.570796327) nzd))
(setq pt7 (polar pt6 (- ang 3.141592654) nzl))
(setq pt8 (polar pt7 (+ ang 1.570796327) (/ nzd 2)))
(command "pline" pt1 "w" 0 0 pt3 pt4 pt5 pt6 pt7 pt8 "")
;第一个画完 (princ)
) 各点坐标值没问题，但就是小段线有时不画，是精度问题？我从网上下载过一个画截断线的lisp程序也有类似问题，请高手解答！

f5612140

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