Hello,
i look for a portable way to determine the return-type of a member function:
#include
#include
class CMyClass
{
public:
int method( void ) {return 5;}
};
template< typename T >
struct result_of
{};
template< typename R, typename A >
struct result_of< R(*)(A) >
{
typedef R type;
};
template< typename R >
struct result_of< R(*)(void) >
{
typedef R type;
};
template< typename R, typename C >
struct result_of< R(C::*)(void) >
{
typedef R type;
};
template< typename R, typename C, typename A >
struct result_of< R(C::*)(A) >
{
typedef R type;
};
/*...some other specialisations...*/
/* (1) OK, but I must now return-type and signature */
//typedef int (CMyClass::*fnPointer_t)(void);
/* (2) OK, but I must now return-type and signature */
//typedef typeof(int(CMyClass::*)(void)) fnPointer_t;
/* (3) OK, compiler determine return-type and signature if CMyClass::method non-ambiguous */
typedef typeof(&CMyClass::method) fnPointer_t;
int main( )
{
fnPointer_t p = &CMyClass::method;
/* (4) OK */
result_of< fnPointer_t >::type i;
/* (5) OK, if CMyClass::method non-ambiguous */
result_of< typeof(&CMyClass::method) >::type i2;
/* (6) Failure, type expected */
//result_of< p >::type i3;
/* (7) OK */
result_of< typeof(p) >::type i4;
/* (8) Failure, no function pointer support */
//boost::result_of< fnPointer_t >::type i5;
/* (9) Failure, no function pointer support */
//boost::result_of< typeof(&CMyClass::method) >::type i6;
/* (10) Failure, no function pointer support */
//boost::function_traits< fnPointer_t >::result_type i7;
/* (11) Failure, no function pointer support */
//boost::function_traits< typeof(&CMyClass::method) >::result_type i8;
}
Which is a portable way? My prefered solution is number 5, but i dont now whether typeof(&CMyClass::method) is portable.
Why function pointer are not supported by boost::result_of and boost::function_traits templates?
Thanks and Greetings,
Peter
