Re: [Boost-users] Converting loop to using boost::lambda where containers has boost::shared_ptrs

From: Nat Goodspeed (ngoodspeed_at_[hidden])
Date: 2007-05-19 14:36:03

> -----Original Message-----
> From: boost-users-bounces_at_[hidden] [mailto:boost-users-
> bounces_at_[hidden]] On Behalf Of Stephen Torri
> Sent: Saturday, May 19, 2007 12:58 PM
> To: boost-users_at_[hidden]
> Subject: Re: [Boost-users] Converting loop to usingboost::lambda where
> containers has boost::shared_ptrs
> 
> Here is a test program that represents the problem we are trying to
> solve. 
> 
>     std::for_each ( m_data.begin(),
>                     m_data.end(),
>                     std::cout << boost::bind ( &Base::to_String,
>                                                boost::bind::_1,
>                                                indent_value ) );

[Nat] Heh. With my VC 7.1 compiler (Version 13.10.3077 according to cl
/help), the program you sent produces an ICE. But then I'm still on
Boost 1.31.1.

On the other hand, since the program you sent makes no mention
whatsoever of boost::lambda, you can remove the boost::bind
qualification from _1 because there's no ambiguity. I did that, and got
an error about trying to insert a boost::bind() expression to std::cout.
Which would sort of toss us back towards boost::lambda.

I thought I'd try using boost::bind on the insertion operator anyway:

    std::for_each ( m_data.begin(),
                    m_data.end(),
                    boost::bind(operator<<, boost::ref(std::cout),
                                boost::bind ( &Base::to_String,
                                              _1,
                                              indent_value ) ));

but the compiler wasn't buying it.

So... maybe there's a way to express what I was trying to write above,
or maybe there's a way to express Stuart's boost::lambda::bind
construct.

But for myself, in this situation I'd consider an explicit 'for' loop
the clearest expression of intent.

C++ is a truly amazing language that, in many cases, *almost* gets you
where you want to go. :-)