Krzysztof Czainski wrote:
2013/2/11 Andrew Hundt <athundt@gmail.com>
Generally, built-in types are initialized when the constructor is called explicitly. For example:
int a; // a has the value of underlying memory int b = int(); // b has a value of 0
Right now the default behavior of our container is more like a vector than an array when creating values using the default ctor. Default constructable values are explicitly initialized in the varray ctor, resize(), emplace() and emplace_back() functions, even when they are trivially constructable. We find this behavior more intuitive and therefore we have made it the default. If the performance needs to be improved slightly the behavior may be changed or disabled in container_detail::varray_traits<V, C, S>.
I assume I can't change the Strategy or emplace_back()/resize() behavior for just one particular varray object, can I?
I mean:
varray<int,5> a; varray<int,5> b;
I'd like to change the Strategy only for b, can I do that?
You may do it by partially specialize varray_traits for your strategy. Currently the varray allowing to pass user-defined strategy is implemented in the container_detail namespace. So it would look more or less like this: namespace bc = boost::container; // define my strategy template <typename V> struct my_strategy : public bc::container_detail::strategy::def<V> {}; // specialize traits for my strategy namespace boost { namespace container { namespace container_detail { template <typename V, typename C> struct varray_traits<V, C, my_strategy> : public varray_traits<V, C, strategy::def<V> > { typedef boost::true_type disable_trivial_init; }; }}} /*...*/ // use non-default version of varray bc::container_detail::varray<int, 5, my_strategy<int> > b; Future alternative: Currently settings like disable_trivial_init are hidden deeply inside details. However they might be a part of default Strategy concept. Assuming that varray was moved to the boost::container namespace the example would be shorter: // define my strategy template <typename V> struct my_strategy : public bc::strategy::def<V> { typedef boost::true_type disable_trivial_init; }; /*...*/ // use non-default version of varray bc::varray<int, 5, my_strategy<int> > b; Regards, Adam