我有以下代码:
std::vector<PriceQuote, tbb::scalable_allocator<PriceQuote> > cBids(maxSize);
std::vector<PriceQuote, tbb::scalable_allocator<PriceQuote> > cAsks(maxSize);
auto zipBidsAsks = boost::make_zip_iterator(boost::make_tuple(cBids.begin(), cAsks.begin()));
如果我想decltype
返回值,那么我可以将其存储在auto
的{{1}}个decltype
中,而不是将其存储在boost::make_zip_iterator
中。那段代码是什么样的?
我试过了:
typedef decltype(boost::make_zip_iterator(std::vector<PriceQuote>, std::vector<PriceQuote>)) zipper_type;
// type referred to by zipper_type::iterator
typedef std::iterator_traits<zipper_type::iterator>::value_type zipped_type;
zipped_type zipBidsAsks = boost::make_zip_iterator(boost::make_tuple(cBids.begin(), cAsks.begin()));
但这甚至没有接近工作。最后,如果我想迭代zipBidsAsks
并获取每个<0>
,<1>
。怎么做的?
访问代码现在出错:
struct PriceBookEventData
{
timeval ts;
unsigned totalSize;
unsigned maxSize;
typedef decltype
(
boost::make_zip_iterator(boost::tuple<std::vector<PriceQuote>::iterator,
std::vector<PriceQuote>::iterator>())
) zipper_type;
zipper_type zipBidsAsks;
};
void AGUI::HandlePriceBookChange(const PriceBookEventData pbed)
{
int k = 0;
while(0 != stop--)
{
PriceQuote pqb = boost::get<0>(pbed.zipBidsAsks[k]);
PriceQuote pqa = boost::get<1>(pbed.zipBidsAsks[k]);
/data/cbworkspace/AGUI/AGUI.cpp|101|error: no matching function for call to ‘get(boost::detail::operator_brackets_result<boost::zip_iterator<boost::tuples::tuple<__gnu_cxx::__normal_iterator<PriceQuote*, std::vector<PriceQuote> >, __gnu_cxx::__normal_iterator<PriceQuote*, std::vector<PriceQuote> > > >, boost::tuples::cons<PriceQuote&, boost::tuples::cons<PriceQuote&, boost::tuples::null_type> >, boost::tuples::cons<PriceQuote&, boost::tuples::cons<PriceQuote&, boost::tuples::null_type> > >::type)’|
答案 0 :(得分:3)
我不确定为什么要使用decltype
而不是auto
来确定类型,后者是专门为此类案例设计的。使用decltype
代替繁琐。
你接近你所尝试的内容,除了你给了boost::make_zip_iterator
一对向量,而不是tuple
向量处理器。
试试这个
typedef decltype(
boost::make_zip_iterator(
boost::tuple<
std::vector<PriceQuote>::iterator,
std::vector<PriceQuote>::iterator>()
)
) zipper_type;
至于迭代zip迭代器,这是一个简单的例子:
#include <iostream>
#include <boost/iterator/zip_iterator.hpp>
#include <boost/tuple/tuple.hpp>
#include <vector>
int main()
{
std::vector<int> v1{1,2,3,4}, v2{10,20,30,40};
std::for_each(
boost::make_zip_iterator(boost::make_tuple(v1.begin(), v2.begin())),
boost::make_zip_iterator(boost::make_tuple(v1.end(), v2.end())),
[]( boost::tuple<int, int> const& tup ) {
std::cout
<< boost::get<0>(tup)
<< ", "
<< boost::get<1>(tup)
<< std::endl;
}
);
}
输出:
1, 10
2, 20
3, 30
4, 40