Re: [Boost-users] [bind] using bind for << to ostream

From: Darren Garvey (lists.drrngrvy_at_[hidden])
Date: 2007-06-20 12:30:47

Hi Mojmir,

On 20/06/07, Mojmir Svoboda <mojmir.svoboda_at_[hidden]> wrote:
>
> Hello,
>
> i want to use bind to create a pair and forward it to an std::ostream, i.e.
> like:
>
>     std::for_each(vec.begin(), vec.end(),
>                 bind(&write,
>                     std::cout,
>                     bind(constructor<std::pair<value_t, value_t> >(), _1,
> _1)));
>
> but the compiler says:
>     ios_base.h:781: error: 'ios_base(const ios_base &)' is private
>     boost/boost/lambda/detail/bind_functions.hpp:472: error: within this
> context
>     boost/boost/lambda/detail/function_adaptors.hpp: In static member
> function
>        `static void boost::lambda::function_adaptor<
>             void (*)(ostream &, const pair<value_t, value_t> &)
>         >::apply(
>                 void (*)(ostream &, const pair<value_t, value_t> &),
>                 const ostream &,
>                 const pair<value_t, value_t> &)'
>         ...
> it seem that temporary is created? why? how to avoid it?

Have you tried:

 std::for_each(vec.begin(), vec.end(),
                bind(&write,
                    boost::ref(std::cout),  // !!
                    bind(constructor<std::pair<value_t, value_t> >(), _1,
_1)));

?

That stops bind taking a copy of std::cout, which should fix the first
problem.

-- 
Darren