From: John Maddock (john_maddock_at_[hidden])
Date: 2002-11-29 06:45:13
> I'm trying to use the function traits to extract the return type of a
template parameter,
> but it's not compiling.
>
> Any ideas what's wrong here?
Yes, function_traits takes a function type as parameter, *not* a function
pointer type:
function_traits<int (int, double)> // OK
function_traits<int (*)(int, double)> // not OK.
So throw in a remove_pointer into your code and everything should be well:
> -------- begin simplified code ------
>
template<typename Proc>
class CacheValue {
typedef boost::remove_pointer<Proc>::type np_type;
typedef boost::function_traits<np_type>::R ReturnType;
template<typename Arg1>
ReturnType operator () ( Arg1 arg1 ) { /* do something */ }
};
CacheValue<unsigned long (*) ( unsigned long )> aValue;
> -------- end simplified code ------
John Maddock
http://ourworld.compuserve.com/homepages/john_maddock/index.htm