Re: [Boost-users] function object wrapper problem

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2005-08-29 21:46:57

On Aug 29, 2005, at 4:44 PM, Okko Willeboordse wrote:

> Peter Dimov wrote:
>> Okko Willeboordse wrote:
>>
>>
>>> So I do
>>>
>>> class some_class
>>> {
>>> public:
>>>   template <class T>
>>>   some_class(const boost::function1<T*, short*>& get_member)
>>
>>
>> Why not just
>>
>>     template<class F> some_class( F f );
>>
>> ?
>>
>> boost::function<> is useful when you have to capture an arbitrary 
>> function
>> object in a fixed type. Since your boost::function<> above is 
>> templated on
>> T, it has a variable type, so you can just use the function object 
>> argument
>> as-is.
>
> Thanks,
>
> Then I end up with a constructor that takes any type of data which
> can not be distinguished from my other constructors.

I'm not sure what your other constructors look like, but perhaps you 
could constrain F such that there is no question that the templated 
constructor will accidently bind to the wrong call.  For example:

class some_class
{
public:
   some_class(int i);
   template <class T>
      template<class F> some_class( F f, typename 
enable_if<!is_convertible<F, int>::value>::type* = 0);
};

-Howard