Hi Gordon,
So, here's something complete (?) for people to rip apart:
int i = convert_cast<int>(s); // default behavior: might throw optional<int> i = convert_cast<int>(s, use_optional_instead_of_throwing_); int i = convert_cast<int>(s, 17); // won't throw; can't tell if conversion successful int i = convert_cast<int>(s, 17, throw_even_though_i_specified_a_failback_); optional<int> i = convert_cast<int>(s, 17, use_optional_instead_of_throwing_); pair<bool,int> i = convert_cast<int>(s, 17, fallback_and_report_success_);
I am not concerned with names, just with syntax. So I'm using "convert_cast" although I actually don't care what it's called, and I have some very ugly very descriptive tag values with distinct types to trigger different overloads, which might be abbreviated dont_throw_, do_throw_, and, um, tell_fallback_ or something.
All would also accept extra manip_/format_= and locale_ arguments as in Vladimir's proposal, except they have to be appended to the first parameter list because of the "no proxies" requirement.
Doesn't this now cover all the functionality we've been talking about?
Since there are now a bunch of overloads with different behavior, and no converter<> object, I figure these would dispatch to a customization point function that looks a lot like Vicente's, but probably with a default an extra bool parameter indicating whether to throw.
Sounds good. What about: int i = convert_cast<int>(s); // agreed optional<int> i = convert_cast<optional<int> >(s); // so optional indicated in template parameter as return type - as always int i = convert_cast<int>(s, 17); // agreed int i = convert_cast<int, throw_even_though_i_specified_a_failback_>(s, 17); // template parameter as optional one there optional<int> i ... (similar as other one with optional) pair<bool, int> i = convert_cast<pair<bool, int> >(s, 17); // pair indicated in template parameter This would never need any runtime parameter -> dispatching possible on compile-time -> no if's or cases necessary in implementation. And it always returns the type is in the (first) template parameter of convert. Regards, Barend