Re: [Boost-users] [fusion] adapted std::pair and ostream

Subject: Re: [Boost-users] [fusion] adapted std::pair and ostream
From: Joel de Guzman (joel_at_[hidden])
Date: 2011-07-19 19:06:14

On 7/19/2011 6:28 PM, Daniel James wrote:
> Hi
> 
> The docs:
> 
> http://www.boost.org/doc/libs/1_47_0/libs/fusion/doc/html/fusion/adapted/std__pair.html
> 
> seem to suggest that one can pipe an adapted std::pair 'directly' to cout.
> 
> I find the following though:
> 
> #include <iostream>
> #include <boost/fusion/adapted.hpp> // adapt pair.
> #include <boost/fusion/sequence.hpp>  // operator<<() ?
> #include <boost/fusion/container.hpp> // as_vector
> 
> int main(int argc, char** argv)
> {
>     std::pair<std::string, int> p("foo", 7);
> 
>     std::cout << p << std::endl;    // does not compile although docs
> suggest it should.
>     std::cout << boost::fusion::as_vector(p) << std::endl;   //
> compiles and works as expected.
> 
>     return 0;
> }
> 
> Am I missing an include? Is sending to cout without first using
> as_vector actually supported?

No, it can't compile. It will only compile if ADL pickus up the << from
boost::fusion, but it can't do that because pair is in namespace std.
Could you point me to the docs where it says it should? It's probably
a doc bug.

Regards,
-- 
Joel de Guzman
http://www.boostpro.com
http://boost-spirit.com