[英]Check if iterator's type is reverse_iterator
Is there a way to check if iterator passed as arg to fnc is reverse_iterator? 有没有办法检查作为arg传递给fnc的迭代器是否为reverse_iterator? Are there any iterator traits function I could use?
我可以使用任何迭代器特征功能吗?
It's trivial to write with a partial specialization: 编写部分专业化的内容很简单:
#include <iterator>
#include <type_traits>
template<typename Iter>
struct is_reverse_iterator
: std::false_type { };
template<typename Iter>
struct is_reverse_iterator<std::reverse_iterator<Iter>>
: std::true_type { };
Although as pointed out below, this doesn't handle the (IMHO unlikely) case of a "reverse-reverse" iterator. 尽管如下所述,但这不能处理“反向-反向”迭代器的情况(恕我直言,不太可能)。 The slightly less trivial version in Bathsheba's answer handles that case correctly.
Bathsheba的回答中的琐碎版本略少一些,可以正确处理这种情况。
Some code I use in production: 我在生产中使用的一些代码:
#include <iterator>
#include <type_traits>
template<typename I>
struct is_reverse_iterator : std::false_type
{
};
template<typename I>
struct is_reverse_iterator<std::reverse_iterator<I>>
: std::integral_constant<bool, !is_reverse_iterator<I>::value>
{
};
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