Boost<boost/any.hpp>
有:
template<typename ValueType>
ValueType any_cast(any & operand);
template<typename ValueType>
inline ValueType any_cast(const any & operand);
(在其他变体中。)这种组合不应该在调用中引起歧义boost::any_cast<int>(my_any);
吗?
我问是因为如果我写这个程序:
#include <boost/any.hpp>
#include <iostream>
template<typename ValueType>
ValueType any_cast(boost::any & operand)
{
return boost::any_cast<ValueType>(operand);
}
int main()
{
int x = 123;
boost::any my_any(x);
std::cout << "my_any = " << any_cast<int>(my_any) << "\n";
return 0;
}
我确实收到了关于歧义的投诉:
g++ -std=c++14 -O3 -Wall -pedantic -pthread main.cpp && ./a.out
main.cpp: In function 'int main()':
main.cpp:14:57: error: call of overloaded 'any_cast(boost::any&)' is ambiguous
std::cout << "my_any = " << any_cast<int>(my_any) << "\n";
^
main.cpp:5:11: note: candidate: ValueType any_cast(boost::any&) [with ValueType = int]
ValueType any_cast(boost::any & operand)
^~~~~~~~
In file included from main.cpp:1:0:
/usr/local/include/boost/any.hpp:281:22: note: candidate: ValueType boost::any_cast(const boost::any&) [with ValueType = int]
inline ValueType any_cast(const any & operand)
^~~~~~~~
/usr/local/include/boost/any.hpp:258:15: note: candidate: ValueType boost::any_cast(boost::any&) [with ValueType = int]
ValueType any_cast(any & operand)
^~~~~~~~