我正在尝试使用以下代码在一个类上检测运算符,该代码不适用于 sfinae,任何专家都对我所缺少的内容有任何想法。
当您在尝试检测它的类型上删除运算符 + 时,编译器也会死亡
template<class T1, class T2>
class has_addition_operator
{
private:
typedef char no;
static auto has(T1* a, T2* b) -> decltype( *a + *b);
static char has(...);
public:
enum{
value = (sizeof( has(new T1(), new T2())) != sizeof(no))
};
};
struct point{
int x, y;
point operator + (point const & o){
point r = *this;
r.x += o.x;
r.y += o.y;
return r;
}
};
bool has = liboperator::has_addition_operator<point,point>::value;
编译器具有以下输出:
1>------ Build started: Project: liboperator, Configuration: Debug Win32 ------
1> liboperator.cpp
1>c:\projects\liboperator\liboperator\liboperator\has_addition_operator.h(15): error C2784: 'std::_String_iterator<_Mystr> std::operator +(_String_iterator<_Mystr>::difference_type,std::_String_iterator<_Mystr>)' : could not deduce template argument for 'std::_String_iterator<_Mystr>' from 'point'
1> c:\program files (x86)\microsoft visual studio 11.0\vc\include\xstring(420) : see declaration of 'std::operator +'
1> c:\projects\liboperator\liboperator\liboperator\liboperator.cpp(26) : see reference to class template instantiation 'liboperator::has_addition_operator<T1,T2>' being compiled
1> with
1> [
1> T1=point,
1> T2=point
1> ]
1>c:\projects\liboperator\liboperator\liboperator\has_addition_operator.h(15): error C2784: 'std::_String_const_iterator<_Mystr> std::operator +(_String_const_iterator<_Mystr>::difference_type,std::_String_const_iterator<_Mystr>)' : could not deduce template argument for 'std::_String_const_iterator<_Mystr>' from 'point'
1> c:\program files (x86)\microsoft visual studio 11.0\vc\include\xstring(288) : see declaration of 'std::operator +'
1>c:\projects\liboperator\liboperator\liboperator\has_addition_operator.h(15): error C2784: 'std::move_iterator<_RanIt> std::operator +(_Diff,const std::move_iterator<_RanIt> &)' : could not deduce template argument for 'const std::move_iterator<_RanIt> &' from 'point'
1> c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1947) : see declaration of 'std::operator +'
1>c:\projects\liboperator\liboperator\liboperator\has_addition_operator.h(15): error C2784: 'std::_Array_iterator<_Ty,_Size> std::operator +(_Array_iterator<_Ty,_Size>::difference_type,std::_Array_iterator<_Ty,_Size>)' : could not deduce template argument for 'std::_Array_iterator<_Ty,_Size>' from 'point'
1> c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1801) : see declaration of 'std::operator +'
1>c:\projects\liboperator\liboperator\liboperator\has_addition_operator.h(15): error C2784: 'std::_Array_const_iterator<_Ty,_Size> std::operator +(_Array_const_iterator<_Ty,_Size>::difference_type,std::_Array_const_iterator<_Ty,_Size>)' : could not deduce template argument for 'std::_Array_const_iterator<_Ty,_Size>' from 'point'
1> c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1662) : see declaration of 'std::operator +'
1>c:\projects\liboperator\liboperator\liboperator\has_addition_operator.h(15): error C2784: 'std::reverse_iterator<_RanIt> std::operator +(_Diff,const std::reverse_iterator<_RanIt> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'point'
1> c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1226) : see declaration of 'std::operator +'
1>c:\projects\liboperator\liboperator\liboperator\has_addition_operator.h(15): error C2784: 'std::_Revranit<_RanIt,_Base> std::operator +(_Diff,const std::_Revranit<_RanIt,_Base> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'point'
1> c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1031) : see declaration of 'std::operator +'
1>c:\projects\liboperator\liboperator\liboperator\has_addition_operator.h(15): error C2676: binary '+' : 'point' does not define this operator or a conversion to a type acceptable to the predefined operator
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========