这是我写的一个示例：
# Make an example list
l <- list(data.frame(a = 1:3, b = 4:6), data.frame(a = 7:8, b = 8:9))
l
#> [[1]]
#> a b
#> 1 1 4
#> 2 2 5
#> 3 3 6
#>
#> [[2]]
#> a b
#> 1 7 8
#> 2 8 9
# Get a dataframe from it
df <- do.call('rbind', l)
# Add the element numbers by repeating the indices of the list,
# each as many times as the number of rows in that element's dataframe
df$element_number <- rep(seq_along(l), times = sapply(l, nrow))
df
#> a b element_number
#> 1 1 4 1
#> 2 2 5 1
#> 3 3 6 1
#> 4 7 8 2
#> 5 8 9 2
为什么private void MainForm_Load(object sender, EventArgs e)
{
int cusLooper = 0;
int assyLooper = -1;
//Load xml
XmlDocument db = new XmlDocument();
db.Load("XML Template.xml");
XmlNodeList nl = db.GetElementsByTagName("Customer");
foreach (XmlNode node in nl)
{
XmlNode element = node;
foreach(XmlNode node2 in node)
{
XmlNode node3 = node2;
if (node2.Name == "Name")
{
treeView1.Nodes.Add(node3.InnerText);
assyLooper = -1;
}
foreach (XmlNode node4 in node3)
{
if (node4.Name == "AssemblyNumber")
{
treeView1.Nodes[cusLooper].Nodes.Add(node4.InnerText);
assyLooper++;
}
if (node4.Name == "Part")
{
XmlNode element2 = node4;
foreach (XmlNode final in element2)
{
if (final.Name == "PartNumber")
{
TreeNode nd = treeView1.Nodes[cusLooper].Nodes[assyLooper].Nodes.Add(final.InnerText);
nd.ImageIndex = 7;
nd.SelectedImageIndex = nd.ImageIndex;
}
}
//assyLooper++;
}
}
}
cusLooper++;
}
}
尝试构造一个新对象struct Foo
{
Foo() = default;
Foo(int)
{
};
};
int main()
{
int baz = 10;
Foo(1); // OK
Foo(baz); // Fails, redefinition
return 0;
}
，而不是构造一个将参数Foo(baz)传递给构造函数的匿名对象？当我通过编写baz来声明对象baz时，我得到了一个很好的默认初始化对象，但是一旦尝试传递参数，它就会失败。如何解决歧义？
答案 0 :(得分：5)
Foo(baz);等效于Foo baz;，这显然是一个声明。
并且由于baz早已在相同范围中声明为类型int的局部变量，因此会出现重新定义错误。