[编程交流] 偏移x单位并移动

(defun c:test (/ n ss p e); 1. what the switch / means?
(if
   (and (setq n (getdist "\n Specify the Offset Distance 
:"));2.what the use of "and" 
here?
(setq
          ss (ssget 
"_+.:S:L" '((0 . "*POLYLINE,*LINE,CIRCLE,ELLIPSE")));3. select all 
polys,line,circle,elipse andd  put them in ss 
variable?
)
        (setq p (getpoint "\n 
Specify point :"))
   )
(progn
      (command "_.offset" n ss "_non" p 
"");4.offset all shapes?
      (setq e 
(entlast))
      (if (tblsearch "LAYER" 
"cover");.5???
        (command 
"_.chprop" e "" "_layer" "cover" 
"");.6???
      )
)
    (princ)
 )
 (princ)
)