Question

我想将Boost phoenix成员函数运算符用于具有重载的类函数，例如here。

以下示例失败：

#include <boost/phoenix/phoenix.hpp>
#include <boost/phoenix/operator.hpp>

using namespace std;
using namespace boost::phoenix::placeholders;

struct A
{
    int m_id = 1;
    int func() const { return 1; }
    void func(int id) { m_id = id; }
};

int main()
{
    A *a = new A;
    auto retVal = (arg1->*&A::func)()(a);

    return 0;
}

有错误：

    In function 'int main()': 17:21: error: no match for 'operator->*'
(operand types are 'const type {aka const
boost::phoenix::actor<boost::proto::exprns_::basic_expr<boost::proto::tagns_::
tag::terminal, boost::proto::argsns_::term<boost::phoenix::argument<1> >, 0l> 
>}' and '<unresolved overloaded function type>') 17:21: note: candidate is: In
 file included from /usr/include/boost/phoenix/operator/arithmetic.hpp:13:0,
 from /usr/include/boost/phoenix/operator.hpp:13, from /usr/include/boost
/phoenix/phoenix.hpp:13, from 1: /usr/include/boost/proto/operators.hpp:295:9:
 note: template<class Left, class Right> const typename 
boost::proto::detail::enable_binary<boost::proto::domainns_::deduce_domain, 
boost::proto::detail::not_a_grammar, 
boost::mpl::or_<boost::proto::is_extension<Arg>, 
boost::proto::is_extension<Right> >, boost::proto::tagns_::tag::mem_ptr, const
 Left&, const Right&>::type boost::proto::exprns_::operator->*(Left&&, 
Right&&) BOOST_PROTO_DEFINE_OPERATORS(is_extension, deduce_domain) ^ 
/usr/include/boost/proto/operators.hpp:295:9: note: template argument 
deduction/substitution failed: 17:28: note: couldn't deduce template parameter 
'Right'

但是，如果我将void func(int id) { m_id = id; }行注释掉，它将按预期工作。

如何确定要使用哪些重载？

Answer 1

处理（成员）函数指针以重载集总是很痛苦的。您需要将地址强制转换为具有所需重载确切签名的指针。对于您的情况，选择int A::func()：

auto retVal = (arg1->*static_cast<int (A::*)() const>(&A::func))()(a);

或更具可读性，但基本相同：

const auto memFctPtr = static_cast<int (A::*)() const>(&A::func);
auto retVal = (arg1->*memFctPtr)()(a);

如果函数有重载，Boost phoenix成员函数运算符将无法编译

1 个答案: