BOOST_FUSION_ADAPT_TPL_STRUCT和模板数组大小 [英] BOOST_FUSION_ADAPT_TPL_STRUCT and template array size

问题描述

我想一个C ++模板结构感谢<一个迭代href=\"http://www.boost.org/doc/libs/1_53_0/libs/fusion/doc/html/fusion/adapted/adapt_tpl_struct.html\"相对=nofollow> BOOST_FUSION_ADAPT_TPL_STRUCT 。我的结构包含固定大小的多维数组的大小是模板参数。如果我们考虑到Boost的例子修改，以适应我的问题：

I am trying to iterate over a C++ template structure thanks to BOOST_FUSION_ADAPT_TPL_STRUCT. My structure contains fixed-size multidimensional arrays whose sizes are template parameters. If we consider Boost's example modified to fit my problem:

#include <iostream>
#include <string>
#include <boost/fusion/adapted/struct/adapt_struct.hpp>
#include <boost/fusion/include/adapt_struct.hpp>

// Example:
// http://www.boost.org/doc/libs/1_53_0/libs/fusion/doc/html/fusion/adapted/adapt_tpl_struct.html

namespace demo
{
    template<typename T, unsigned int SIZE1, unsigned int SIZE2, typename Name, typename Age>
    struct employee
    {
        Name name;
        Age age;
        T ar[SIZE1][SIZE2];
    };
}

// Any instantiated demo::employee is now a Fusion sequence
BOOST_FUSION_ADAPT_TPL_STRUCT(
    (T)(SIZE1)(SIZE2)(Name)(Age),
    (demo::employee) (T)(SIZE1)(SIZE2)(Name)(Age),
    (Name, name)
    (Age, age)
    (T, ar[SIZE1][SIZE2]))

int main()
{
    demo::employee<float, 2, 2, std::string, int> e;
    e.name = "Bob";
    e.age = 25;
    e.ar[0][0] = e.ar[1][0] = 0.1;
    e.ar[0][1] = e.ar[1][1] = 0.2;
}

编译失败。此外，它还如果我们只添加一个整数模板参数，甚至没有使用它的数组的大小失败。

The compilation fails. Moreover, it also fails if we only add an integer template parameter without even using it for the array size.

是，即使是可能的 BOOST_FUSION_ADAPT_TPL_STRUCT ？如果不是这样，我应该怎么去呢？

Is that even possible with BOOST_FUSION_ADAPT_TPL_STRUCT? If not, how should I go about this?

推荐答案

从<一个href=\"http://www.boost.org/doc/libs/1_53_0/libs/fusion/doc/html/fusion/adapted/adapt_tpl_struct.html\"相对=nofollow> DOC ：

序列（template_param0）（template_param1）...宣布在模板类型参数的名称使用。

The sequence (template_param0)(template_param1)... declares the names of the template type parameters used.

虽然你有非类型模板参数 尺寸：

template<typename T, unsigned int SIZE, typename Name, typename Age>
struct employee

您可以将其转换为键入模板参数和使用的 的boost :: MPL :: INT _ 作为包装适合随身携带的大小。

You may convert it to type template parameter and use boost::mpl::int_ as wrapper for carry size.

现在，您的code是 编译 。

Now, your code is compiled.

template<int Size>
struct Array
{
    template<typename T>
    struct Of
    {
        typedef T type[Size];
    };
};

namespace demo
{
    template<typename T, typename SIZE, typename Name, typename Age>
    struct employee
    {
        Name name;
        Age age;
        T ar[SIZE::value];
    };
}

// Any instantiated demo::employee is now a Fusion sequence
BOOST_FUSION_ADAPT_TPL_STRUCT(
    (T)(SIZE)(Name)(Age),
    (demo::employee) (T)(SIZE)(Name)(Age),
    (Name, name)
    (Age, age)
    (typename Array<SIZE::value>::template Of<T>::type, ar))

 //...
 demo::employee<float, int_<2>, std::string, int> e;

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