Re: [Boost-users] [fusion] "real" return types

Subject: Re: [Boost-users] [fusion] "real" return types
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2009-08-19 18:28:07

AMDG

Stefan Strasser wrote:
> I have a problem with boost.fusion I can't figure out from the documentation.
>
> consider the following example:
>
> template<class Vector>
> ? function(Vector vec){
> 	return fusion::push_back(vec,123);
> }
>
> what is the return type ?
> the return type is supposed to be a random access sequence, so 
> result_of::push_back<Vector,int>::type is not an option, because push_back 
> only returns a forward sequence.
> so I have to construct a new vector from the view that push_back returns.
> if Vector was vector<char,short> I need to find the type 
> vector<char,short,int>, preferrably without an own MPL algorithm since this 
> is only a simple test case, the real return type is much more complex and 
> based on more than one transformation function.
>   

you'll need something like this:

typename fusion::result_of::as_vector<
    typename fusion::result_of::push_back<Vector, int>::type
 >::type

In Christ,
Steven Watanabe