Re: [boost] Streaming Lambda functions

From: David Abrahams (dave_at_[hidden])
Date: 2008-07-11 11:41:02

on Fri Jul 11 2008, "Robert Jones" <robertgbjones-AT-gmail.com> wrote:

> Is it possible to invoke user defined streaming operators within boost
> lambda
> functions? In this style
>
> #include <iostream>
> #include <map>
> #include "boost/lambda/lambda.hpp"
>
> using namespace std;
>
> ostream & operator << ( ostream & ostrm, pair<string, string> const & input
> );
>
> ostream & operator << ( ostream & ostrm, map<string, string> & inputs )
> {
>   using namespace boost :: lambda;
>
>   for_each ( inputs.begin( ), inputs.end( ), ostrm << _1 << '\n' );
>   return ostrm;
> }

Yes, something like that works.

> Is this basically undoable, or am I doing it wrong? 

Why would you think either one was true?

Note that std::endl can cause you big troouble, but since you're using
'\n' above I don't see a reason to worry.  You do need something like
"using namespace boost::lambda;" to make "_1" valid, though.

> Also, does the online Comeau compiler understand the boost include
> directives?

That's a question for Comeau.

HTH,

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com