On Mon, Dec 17, 2012 at 4:29 PM, Mark Snelling <mark@bakedbeans.com> wrote:

Hi, I'm not sure if this has already been done but I have created a new Boost.Range adapter that will return a specified member variable of the class in the range, similar to the existing map_keys and map_values adapters. Would there be interest in this?

For example consider the following code:

#include <boost/range/adaptor/member.hpp> #include <boost/range/algorithm/copy.hpp> #include <boost/lexical_cast.hpp> #include <iostream> #include <vector> #include <string>

struct A { int foo; std::string bar; };

int main(int argc, char* argv[]) { std::vector< A > input; for ( int i = 0; i < 10; ++i ) { A a; a.foo = i; a.bar = boost::lexical_cast< std::string >( i * 10 ); input.push_back( a ); }

boost::copy( input | boost::adaptors::selected_member( &A::foo ), std::ostream_iterator< int >( std::cout, "," ) );

std::cout << std::endl;

boost::copy( input | boost::adaptors::selected_member( &A::bar ), std::ostream_iterator< std::string >( std::cout, "," ) );

return 0; }

Cheers,

Mark

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How is this different to input | boost::adaptors::transformed( bind( &A::bar ) ) ? I guess your solution avoids the explicit bind, but if that's an often used shorthand I'd prefer to see a more general solution for transformed, filtered and maybe others that interprets a method or member address in this way when passed as a functor or predicate. - Rob.