[英]Why is std::generate accessible without namespace qualifier?
Is it normal that this compiles fine? 编译好是正常的吗?
#include <vector>
#include <algorithm>
int main()
{
std::vector<int> buf;
generate(buf.begin(), buf.end(), []{ return 0; });
}
(Note the missing std::
in front of generate()
) (注意在generate()
前面缺少的std::
Is this behavior documented somewhere? 这种行为是否记录在某处? Or did I stumble across a compiler or library bug? 或者我偶然发现了编译器或库错误? Which in my case would be GCC 5.3.0 and Clang 3.8.0 on Linux; 在我的例子中,在Linux上是GCC 5.3.0和Clang 3.8.0; both use libstdc++, so maybe library bug? 两者都使用libstdc ++,所以也许库bug?
This is allowed, essentially because the arguments to generate
are in std
. 这是允许的,主要是因为generate
的参数是std
。
Code like 代码就像
namespace Foo
{
struct B{};
void foo(const B&);
}
int main()
{
Foo::B b; /*Requires Foo::*/
foo(b); /*Does not require Foo:: as that is gleaned from the argument*/
}
is acceptable for similar reasons. 因类似原因可以接受。 We call it argument dependent lookup . 我们称之为参数依赖查找 。 See https://en.wikipedia.org/wiki/Argument-dependent_name_lookup 请参阅https://en.wikipedia.org/wiki/Argument-dependent_name_lookup
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