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将boost参数与operator()一起使用

boost-parameter operator-overloading boost c++

Some programmer dude · 技术社区 · 6 年前

我想将boost参数与重载的调用运算符一起使用( operator() ):

#include <string>
#include <boost/parameter/keyword.hpp>
#include <boost/parameter/preprocessor.hpp>

struct add_argument_tag
{
    struct name_;
    struct descr_;
};

static inline boost::parameter::keyword<add_argument_tag::name_>&  name  = boost::parameter::keyword<add_argument_tag::name_>::get();
static inline boost::parameter::keyword<add_argument_tag::descr_>& descr = boost::parameter::keyword<add_argument_tag::descr_>::get();

struct config
{
    BOOST_PARAMETER_MEMBER_FUNCTION(
        (config),
        operator(),
        add_argument_tag,
        (required (name_, (std::string const&)))
        (optional
            (descr_, (std::string const&), "")
        )
    )
    {
        return *this;
    }
};

int main()
{
    config my_config;
    my_config
        ("foo")
        ("bar", descr = "some description");
}

不幸的是,它不起作用:

In file included from /usr/include/boost/mpl/aux_/integral_wrapper.hpp:22,
                 from /usr/include/boost/mpl/int.hpp:20,
                 from /usr/include/boost/mpl/lambda_fwd.hpp:23,
                 from /usr/include/boost/mpl/aux_/na_spec.hpp:18,
                 from /usr/include/boost/mpl/identity.hpp:17,
                 from /usr/include/boost/parameter/aux_/unwrap_cv_reference.hpp:11,
                 from /usr/include/boost/parameter/keyword.hpp:9,
                 from /.../main.cpp:2:
/.../main.cpp:18:18: error: expected unqualified-id before ')' token
         operator(),
                  ^
/.../main.cpp:18:18: error: expected unqualified-id before ')' token
         operator(),
                  ^
/.../main.cpp:18:18: error: expected unqualified-id before ')' token
         operator(),
                  ^
/.../main.cpp:16:5: error: expected nested-name-specifier before 'boost_param_result_24operator'
     BOOST_PARAMETER_MEMBER_FUNCTION(
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /.../main.cpp:3:
/.../main.cpp:16:5: error: expected initializer before '<' token
     BOOST_PARAMETER_MEMBER_FUNCTION(
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/boost/mpl/aux_/integral_wrapper.hpp:22,
                 from /usr/include/boost/mpl/int.hpp:20,
                 from /usr/include/boost/mpl/lambda_fwd.hpp:23,
                 from /usr/include/boost/mpl/aux_/na_spec.hpp:18,
                 from /usr/include/boost/mpl/identity.hpp:17,
                 from /usr/include/boost/parameter/aux_/unwrap_cv_reference.hpp:11,
                 from /usr/include/boost/parameter/keyword.hpp:9,
                 from /.../main.cpp:2:
/.../main.cpp:16:5: error: expected nested-name-specifier before 'boost_param_result_24operator'
     BOOST_PARAMETER_MEMBER_FUNCTION(
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /.../main.cpp:3:
/.../main.cpp:16:5: error: expected initializer before '<' token
     BOOST_PARAMETER_MEMBER_FUNCTION(
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/.../main.cpp:16:5: error: 'boost_param_default_24operator' declared as function returning a function
     BOOST_PARAMETER_MEMBER_FUNCTION(
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/.../main.cpp:16:5: error: 'boost_param_default_24operator' declared as function returning a function
     BOOST_PARAMETER_MEMBER_FUNCTION(
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/boost/mpl/aux_/integral_wrapper.hpp:22,
                 from /usr/include/boost/mpl/int.hpp:20,
                 from /usr/include/boost/mpl/lambda_fwd.hpp:23,
                 from /usr/include/boost/mpl/aux_/na_spec.hpp:18,
                 from /usr/include/boost/mpl/identity.hpp:17,
                 from /usr/include/boost/parameter/aux_/unwrap_cv_reference.hpp:11,
                 from /usr/include/boost/parameter/keyword.hpp:9,
                 from /.../main.cpp:2:
/.../main.cpp:16:5: error: expected nested-name-specifier before 'boost_param_result_24operator'
     BOOST_PARAMETER_MEMBER_FUNCTION(
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /.../main.cpp:3:
/.../main.cpp:16:5: error: expected initializer before '<' token
     BOOST_PARAMETER_MEMBER_FUNCTION(
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/.../main.cpp:16:5: error: 'boost_param_default_24operator' declared as function returning a function
     BOOST_PARAMETER_MEMBER_FUNCTION(
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/.../main.cpp: In function 'int main()':
/.../main.cpp:34:15: error: no match for call to '(config) (const char [4])'
         ("foo")
               ^
make[3]: *** [CMakeFiles/BoostParameterProblem.dir/build.make:63: CMakeFiles/BoostParameterProblem.dir/main.cpp.o] Error 1
make[2]: *** [CMakeFiles/Makefile2:73: CMakeFiles/BoostParameterProblem.dir/all] Error 2
make[1]: *** [CMakeFiles/Makefile2:85: CMakeFiles/BoostParameterProblem.dir/rule] Error 2
make: *** [Makefile:118: BoostParameterProblem] Error 2

我可以通过一个正确命名的函数而不是 运算符() 但是我会的 真的? 喜欢使用 运算符() 在这里。。。:)

我是猜测原因是Boost参数如何使用宏和元编程来构造助手函数等,而使用运算符重载函数是完全不可能的。

有没有人做过这种工作?有可能吗?

1 回复 | 直到 6 年前

llllllllll 6 年前

Boost参数做了很多字符串连接的工作,因此 operator() 将连接到无效的名称。

解决方法之一是委托 运算符() 对其实施。更改宏部分以定义普通函数,然后完美地转发所有参数和最终结果:

struct config
{
    BOOST_PARAMETER_MEMBER_FUNCTION(
        (config),
        myope,
        add_argument_tag,
        (required (name_, (std::string const&)))
        (optional
            (descr_, (std::string const&), "")
        )
    )
    {
        std::cout << name_ << " " << descr_ << "\n";
        return *this;
    }

    template<class... Args>
    decltype(auto) operator() (Args&& ...args) {
        return myope(std::forward<Args>(args)...);
    }
};

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