On Mar 9, 2004, at 12:17 PM, David Abrahams wrote:
Jaakko Jarvi <jajarvi@cs.indiana.edu> writes:
On Mar 9, 2004, at 11:18 AM, David Abrahams wrote:
Lambda docs say:
"When an actual argument is supplied for a placeholder, the parameter passing mode is always by reference"
Yet when I changed the following code from using boost::bind to boost::lambda, I got complaints that Field is an abstract class and can't be copied.
void (self_t::* insert_)(Field const&) = &self_t::insert; std::for_each(fields.begin(), fiends.end(), bind(insert_, this, _1));
What gives?
This requires a bigger fix. BLL uses tuples to manipulate type sequences that are being used in type deduction. In this process, a tuple type containing a non-reference abstract type is formed. Such an object is never instantiated, but it seems that just declaring such a type is not allowed. So the fix is to ditch tuples there, and move to type sequences, which requires quite some coding. Is_abstract may give a quick fix. Jaakko
Can you post (email directly) a full example. I couldn't immediately get similar code to fail.
#include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp>
using namespace boost::lambda;
struct X { virtual void f() = 0; };
struct Y : X { void f() {}; };
struct Z { void g(X const& x) { }
void h(X const& x) { bind(&Z::g, this, _1)(x); } };
-- Dave Abrahams Boost Consulting www.boost-consulting.com
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-- Jaakko Järvi email: jajarvi@cs.indiana.edu -- Post Doctoral Fellow phone: +1 (812) 855-3608 -- Pervasive Technology Labs fax: +1 (812) 855-4829 -- Indiana University, Bloomington