Re: [Boost-users] Comparing boost::function<void()>

From: Doug Gregor (dgregor_at_[hidden])
Date: 2007-05-07 09:05:18

On May 4, 2007, at 7:51 PM, Rennie deGraaf wrote:
> Could anyone please tell me why the following code fails to compile:
>
>> inline void rmfunc(std::list<boost::function<void()> >& funcs,  
>> boost::function<void()> f)
>> {
>>     for (std::list<boost::function<void()> >::iterator  
>> i=funcs.begin(); i!=funcs.end(); ++i)
>>     {
>>         if (boost::function_equal(*i, *f))
>>             i = funcs.erase(i);
>>     }
>> }
>
> while the following does compile:
>
>> template <typename T>
>> inline void rmfunc(std::list<boost::function<void()> >& funcs,  
>> const T& f)
>> {
>>     for (std::list<boost::function<void()> >::iterator  
>> i=funcs.begin(); i!=funcs.end(); ++i)
>>     {
>>         if (boost::function_equal(*i, f))
>>             i = funcs.erase(i);
>>     }
>> }
>
> and seemingly equivalent code, placed in-line in the calling function,
> also compiles?

You cannot compare two boost::function objects directly, because it  
can't be implemented. See the first question on http://www.boost.org/ 
doc/html/function/faq.html

        - Doug