ADAMS命令语言

if cond=(!str_is_space("part_varval(wh)"))
undo begin sup=yes
variable set variable=.mdi.TmpDefOriS str="body313"
defaults unit orientation_type=body123
move rotation part = (eval(".hoisting_system.part_"//ip)) &
csmarker = (eval(".hoisting_system.part_"//wh//".MARKER_1"))&
a1=-15 a2=-3.692839705515409d a3=0.0 about=yes
defaults unit orientation_type = "body313"
undo end
谁能帮我解释一下是什么意思？急用啊