Re: [Boost-users] Type List Iteration?

From: Duane Murphy (duanemurphy_at_[hidden])
Date: 2005-10-04 19:18:40

Darn. I meant to put that in the message. Isn't email supposed to be psychic?

I can't change the base class, hence the problem. It's a very wide
hierarchy  for a framework that I can't change.

Thanks for the suggestion, though.

 ...Duane

--- At Tue, 4 Oct 2005 14:47:29 -0700, Sohail Somani wrote:

>Is there some trouble with defining:
>
>class Base
>{
>	virtual void some_function() = 0;
>};
>
>???
>
>I can understand the void f() entry point for C callbacks but you can
>use C++ to do the work for you. Unless I'm missing something.
>
>> -----Original Message-----
>> From: boost-users-bounces_at_[hidden] 
>> [mailto:boost-users-bounces_at_[hidden]] On Behalf Of Duane Murphy
>> Sent: Tuesday, October 04, 2005 2:38 PM
>> To: Boost Users
>> Subject: [Boost-users] Type List Iteration?
>> 
>> 
>> How do I iterate over a type list and call a function? MPL?
>> 
>> I have a base class BASE that has several subclasses A, B, C 
>> that have special capabilities, but no way to identify those 
>> capabilities aside from the type.
>> 
>> I would like to determine if an object of type BASE is also 
>> of one of the special subclasses:
>> 
>> ie
>> void f( BASE* base)
>> {
>>     if ( dynamic_cast< A* >( base ) != NULL )
>>     {
>>         some_function( dynamic_cast< A* >( base ) );
>>     }
>>     else if ( dynamic_cast< B* >( base ) != NULL )
>>     {
>>         some_function( dynamic_cast< B* >( base ) );
>>     }
>>     else if ( dynamic_cast< C* >( base ) != NULL )
>>     {
>>         some_function( dynamic_cast< C* >( base ) );
>>     }
>> }
>> 
>> I think you can see why I'd like a type list iterator 
>> solution to this. 
>> 
>> I have arranged for the some_function to be a template as 
>> well to make things easier.
>> 
>> What I am looking for is the equivalent of find_if() but for 
>> types and done at run time. I looked over MPL, but MPL seems 
>> to apply at compile time without a door to the run time world. :-)
>> 
>> Thanks for your helpful tips!

 ...Duane