我正在尝试将包装类写入Miranda Conrado提供的笛卡尔乘积迭代器(源代码可以在GitHub上找到)。为了方便起见,我也会在这里引用相关的代码位。
我的类可以用两种方法构造:一种简单,只需将容器转发到product_iterator
构造函数,另一种则比较棘手:它需要许多元组来描述创建容器所需的linspace。然后根据它们构造迭代器。在这里,我走到了尽头。
这是一些代码。
首先,来自Conrado的class product_iterator
的一些相关标头:
// product_iterator.hpp
template <class... Containers>
class product_iterator:
...
public:
product_iterator();
product_iterator(product_iterator const& other);
product_iterator(Containers const&... containers);
~product_iterator();
product_iterator const& operator=(product_iterator const& other);
....
};
template <class... Containers>
product_iterator<Containers...>
make_product_iterator(Containers const&... containers) {
return product_iterator<Containers...>(containers...);
}
这是我的课程:
// gridsearch.hpp
typedef std::unordered_map<std::string, Real> result_type;
typedef std::vector<result_type> resultgrid_type;
template <class... Containers>
class GridSearchIterator {
typedef std::array<std::string,
std::tuple_size<std::tuple<Containers...> >::value>
argname_type;
public:
GridSearchIterator() : product_it(product_iterator<Containers...>()),
argnames(argname_type()) {}
GridSearchIterator(const argname_type& names,
const Containers& ...containers);
template <class... TupleTypes>
static GridSearchIterator<Containers...>
initWith(const TupleTypes&& ...tuples);
template<class F, class... Args>
decltype(auto) iterate(F func, Args&&... params);
private:
template <typename TupleType, size_t... Is>
void product_impl(TupleType&& tuples, std::index_sequence<Is...>);
template <typename TupleType>
const auto& unpack_tuple(TupleType& t, size_t index);
product_iterator<Containers...> product_it;
argname_type argnames;
};
// implementation:
template <class... Containers>
GridSearchIterator<Containers...>::GridSearchIterator(
const argname_type& names,
const Containers& ...containers):
product_it(product_iterator<Containers...>(containers...)),
argnames(names) {}
template <class... Containers>
template <typename... TupleTypes>
GridSearchIterator<Containers...> GridSearchIterator<Containers...>::initWith(const TupleTypes&& ...tuples)
{
GridSearchIterator<Containers...> gsi =
GridSearchIterator<Containers...>();
gsi.product_impl(std::tuple<TupleTypes...>(tuples...),
std::index_sequence_for<TupleTypes...>{});
return gsi;
}
template <class... Containers>
template <typename TupleType, size_t... Is>
void GridSearchIterator<Containers...>::product_impl(TupleType&& tuples,
std::index_sequence<Is...>)
{
product_it = product_iterator<Containers...>(
unpack_tuple(std::get<Is>(tuples), Is)...);
// this is where the problem is; Compiler claims No matching constructor for initialization of 'product_iterator...
}
template <class... Containers>
template <typename TupleType>
const auto& GridSearchIterator<Containers...>::unpack_tuple(TupleType &t,
size_t index)
{
std::string argname;
auto left(0), right(0);
Size step;
std::tie(argname, left, right, step) = t;
argnames[index] = argname;
auto vec = linspace(left, right, step);
return static_cast<const decltype(vec) &>(vec);
}
上面的函数linspace
返回一个从left
到right
的数字向量,该向量由step
的个数均匀隔开。它等效于Numpy函数np.linspace
。
我检查了一下,对unpack_tuple()
的调用的确产生了初始化product_iterator
所需的向量,但是编译器不同意。我的猜测是,unpack_tuple()
返回的类型与product_iterator
构造函数所期望的类型有些不同,但我不知道是什么问题。也许问题实际上出在其他地方。
为了更好地理解,这是我如何使用该类:
{
...
typedef std::tuple<std::string, int, int, size_t> inttuple;
typedef std::tuple<std::string, double, double, size_t> realtuple;
typedef std::vector<int> intvector;
typedef std::vector<Real> realvector;
inttuple sidespan = std::make_tuple("side",1,1,1);
real tuple takeprofit = std::make_tuple("takeprofit",1.,2.,2);
real tuple stoploss = std::make_tuple("stoploss", -1.,-3.,3);
inttuple period = std::make_tuple("horizon", 100, 100, 1);
auto grid_iter = GridSearchIterator<intvector, realvector, realvector, intvector>
::initWith(std::forward<inttuple>(sidespan),
std::forward<realtuple>(takeprofit),
std::forward<realtuple>(stoploss),
std::forward<inttuple>(period));
...
}
我花费了数小时试图解决它,因此任何帮助或指示都将受到高度赞赏,包括有关不同实现的建议。
更新
抱歉,我以为我昨天更新了问题,但是由于某种原因未保存更改。
无论如何,即使没有其他信息,@ max66也回答了该问题。尽管如此,为了完整起见,这里是linspace()
定义
template <typename T>
std::vector<T> linspace(T a, T b, size_t N)
和编译器消息:
在/.../main.cpp:17中包含的文件中:
/.../gridsearch.hpp:98:18:错误:'product_iterator<std::__1::vector<int, std::__1::allocator<int> >, std::__1::vector<double, std::__1::allocator<double> >, std::__1::vector<double, std::__1::allocator<double> >, std::__1::vector<int, std::__1::allocator<int> > >' product_it = product_iterator<Containers...>(unpack_tuple(std::get<Is>(tuples), Is)...);
的初始化没有匹配的构造函数/.../ gridsearch.hpp:91:9:注意:在此处
'GridSearchIterator<std::__1::vector<int, std::__1::allocator<int> >, std::__1::vector<double, std::__1::allocator<double> >, std::__1::vector<double, std::__1::allocator<double> >, std::__1::vector<int, std::__1::allocator<int> > >::product_impl<std::__1::tuple<std::__1::tuple<std::__1::basic_string<char>, int, int, unsigned long>, std::__1::tuple<std::__1::basic_string<char>, double, double, unsigned long>, std::__1::tuple<std::__1::basic_string<char>, double, double, unsigned long>, std::__1::tuple<std::__1::basic_string<char>, int, int, unsigned long> >, 0, 1, 2, 3>'
请求的功能模板特化gsi.product_impl(std::tuple<TupleTypes...>(tuples...), std::index_sequence_for<TupleTypes...>{});
的实例中/.../ main.cpp:90:88:注意:在此处
'GridSearchIterator<std::__1::vector<int, std::__1::allocator<int> >, std::__1::vector<double, std::__1::allocator<double> >, std::__1::vector<double, std::__1::allocator<double> >, std::__1::vector<int, std::__1::allocator<int> > >::initWith<std::__1::tuple<std::__1::basic_string<char>, int, int, unsigned long>, std::__1::tuple<std::__1::basic_string<char>, double, double, unsigned long>, std::__1::tuple<std::__1::basic_string<char>, double, double, unsigned long>, std::__1::tuple<std::__1::basic_string<char>, int, int, unsigned long> >'
要求的功能模板特化auto grid_iter = GridSearchIterator<intvector, realvector, realvector, intvector>::initWith(std::forward<inttuple>(sidespan),
的实例中在/.../main.cpp:17中包含的文件中:
在/.../gridsearch.hpp:22包含的文件中: /.../product_iterator.hpp:73:7:注意:候选构造函数不可行:没有从'vector<int, allocator<int>>' to 'const vector<double, allocator<double>>'
进行第二个参数product_iterator(Containers const&... containers);
的转换
答案 0 :(得分:0)
如果您不提出完整的示例,则很难检查/验证/提出正确的代码。
无论如何,这一行中都会出现错误(“无匹配的构造函数”)
product_it = product_iterator<Containers...>(
unpack_tuple(std::get<Is>(tuples), Is)...);
如果我正确理解的话,Containers...
就是intvector, realvector, realvector, intvector
,也就是std::vector<int>, std::vector<Real>, std::vector<Real>, std::vector<int>
(我认为Real
是double
的别名)。
product_iterator
的唯一可变参数构造函数是接收Containers const&... containers
的变量,所以我想是您要匹配的那个。
在我看来,问题在于unpack_tuple()
template <class... Containers>
template <typename TupleType>
const auto& GridSearchIterator<Containers...>::unpack_tuple(TupleType &t,
size_t index)
{
std::string argname;
auto left(0), right(0);
Size step;
std::tie(argname, left, right, step) = t;
argnames[index] = argname;
auto vec = linspace(left, right, step);
return static_cast<const decltype(vec) &>(vec);
}
返回永远一个intVector const &
(std::vector<int> const &
)。同样,当用realVector
调用时(我想是std::vector<double>
)。
(如果我没记错的话)这是因为您将left
和right
定义为auto
并将它们初始化为int
auto left(0), right(0);
当int
在第二和第三位置包含TupleType
元素时,也会得到一对Real
。
因此,当您获得vec
auto vec = linspace(left, right, step);
您获得(我想)一个std::vector<int>
;曾经以及何时应该获得std::vector<Real>
。
建议:使用取决于left
的正确类型定义right
和TupleType
。
通过示例(警告:代码未经测试)
using lr_type = typename std::tuple_element<1u, TupleType>::type;
lr_type left, right;
从C ++ 14开始,您可以使用std::tuple_element_t
,并且`使用可以简化如下
using lr_type = std::tuple_element_t<1u, TupleType>;
如果可以使用C ++ 17,则可以使用结构化绑定,并且一切都变得简单得多
template <typename TupleType>
const auto& GridSearchIterator<Containers...>::unpack_tuple(TupleType &t,
size_t index)
{
auto [argname, left, right, step] = t;
argnames[index] = argname;
auto vec = linspace(left, right, step);
return static_cast<const decltype(vec) &>(vec);
}
主题外:您确定unpack_tuple()
返回const 引用到在方法执行结束时销毁的值是个好主意吗?