Re: [boost] [gsoc] improving any and variant

Subject: Re: [boost] [gsoc] improving any and variant
From: Hartmut Kaiser (hartmut.kaiser_at_[hidden])
Date: 2009-03-29 23:33:45

> A few little ideas that could eventually be joined to be a single GSoC
> project:
> 
> - Allow visitation for Any. This can actually be generalized to any
> object that exposes a type_info, such as polymorphic objects.
> 
> Techniques, including non-portable ones based on name mangling, could
> be
> experimented to get more efficient dispatch.
> 
> - Add SBO to any.
> 
> - Improve variant so that the functor doesn't require to expose a
> result_type. The result_type can be automatically deduced by "joining"
> all the possible return types obtained by boost::result_of.
> 
> - Allow the easy construction of a visitor from lambda expressions,
> with
> a syntax like
> 
> variant<int, std::string> a = "foo";
> 
> int b = match(a).with(
>     args<int>(_1),
>     args<std::string>(size(_1))
> );
> 
> instead of the potentially more verbose
> 
> struct my_visitor : static_visitor<int>
> {
>      int operator()(int a) { return a; }
>      int operator()(const std::string& b) { return b.size(); }
> };
> 
> variant<int, std::string> a = "foo";;
> 
> int b = apply_visitor(my_visitor(), a);

Please add your ideas to the wiki. That's the place where students will look
first.
Regards Hartmut