Hello Noah, ----- Mensaje original ----- De: Noah Roberts <roberts.noah@gmail.com> Fecha: Miércoles, Noviembre 29, 2006 11:49 pm Asunto: [Boost-users] more lambda issues Para: boost-users@lists.boost.org
I'm kind of loosing faith that this list ever responds to questions but here goes anyway.
I've narrowed a problem down to this:
[...]
std::cerr << "Value: " << (l::bind(&test_b::f, l::_1))(td) << "\n"; [...] Compiler result: cannot instantiate abstract class test_b.
I haven't been following your investigations into the Boost Lambda Library so excuse me if he following is not relevant: your example can be made to work by using boost::reference_wrappers: #include <iostream> #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> #include <boost/ref.hpp> struct test_b { test_b() { std::cerr << "test_b::test_b()\n"; } test_b(test_b const&) { std::cerr << "test_b::test_b(test_b const&) \n"; } virtual int f() = 0; //{ return 5; } }; struct test_d : test_b { test_d() : test_b() { std::cerr << "test_d::test_d()\n"; } test_d(test_d const& d) : test_b(d) { std::cerr << "test_d::test_d(test_d const&)\n"; } int f() { return 5; } }; int main(void) { namespace l = boost::lambda; test_d tdo; test_b & td = tdo; std::cerr << "Value: " << (l::bind(&test_b::f, l::_1))(boost::ref(td)) << "\n"; int x; std::cin >> x; } Another acceptable syntax that does not use reference wrappers is the following: std::cerr << "Value: " << (&l::_1->*&test_b::f)(td)() << "\n"; HTH, Joaquín M López Muñoz Telefónica, Investigación y Desarrollo