dariomt@gmail.com skrev:

Hi list,

I found a small inconvenience while trying to use boost::assign::list_of with the following code

#include <vector> #include <boost/assign/list_of.hpp>

struct A { // no implicit conversion from int explicit A(int i) {}

// constructor from two ints A(int i, int j) {} };

void works_with_two_ints() { std::vector<A> v = boost::assign::list_of<A>(1,2)(3,4)(5,6); }

#if 0 void does_not_work_with_one_int() { std::vector<A> v = boost::assign::list_of<A>(1)(2)(3); } #endif

Looking into the code, it seems as if assign_detail::generic_list<A> had two slightly different versions of operator() generated with some preprocessor magic

// 1) accepts a fully constructed A generic_list& operator()( const A& u ) { this->push_back( u ); return *this; }

// 2) accepts two generic paramenters forwarding them to A's two parameter constructor template <typename U, typename V> generic_list& operator()(const U& u, const V& v) { this->push_back( A(u,v) ); return *this; }

I'm missing another operator() that takes one generic parameter and forwards it to A's one parameter constructor, for the case where it is not implicitly convertible.

// 3) accepts a generic paramenter forwarding it to A's one parameter constructor template <typename U> generic_list& operator()(const U& u) { this->push_back( A(u) ); return *this; }

That saves me from typing A's everywhere

std::vector<A> v = boost::assign::list_of(A(1))(A(2))(A(3));

Does this make sense?

I think it does. Instead of adding a new function, I tried to replace the one argument one. I also tried adding both. It seems to break gcc 4.4 though. Not vc9. So until someone has found a way to make it work on gcc, I'm slightly concerned about adding it. -Thorsten