如果您生成自己的XML对象，xpathSApply中是否存在错误？

I tried the following:

我尝试了以下方法:

library(XML)
top = newXMLNode("A")
newXMLNode("b", attrs=c(x=1,y='abc'),parent=top) 
newXMLNode("c", "With some text", parent=top)
top
xpathSApply(top,'//A/b/@x')
library(XM