Hi Barend, On May 4, 2011, at 9:46 AM, Barend Gehrels wrote:
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.
Yeah, I like that better too. I just wasn't sure exactly how to implement that, since there's a template parameter OutType which is deduced from the argument. But I bet it's possible. The last one points out another big difference between string-to-type and type-to-type: lexical_cast explicitly does not deal with complex types; otherwise that could be ambiguous. (Likewise someone could conceivably want to come up with a string representation of optional<T>.) Either way, it's a job for someone with decent knowledge of Boost.Parameter (not me yet). Cheers! Gordon