Re: [boost] Boost review of the Convert library is ongoing

23 May 2014


      2014-05-23 2:25 GMT+02:00 Vladimir Batov :
[...]

template
...
boost::optional<TypeOut> operator()(TypeIn const&); //#3
surely seems attractive and with that interface converters can be easily
used on their own (if needed/preferred) bypassing "convert" api altogether.
Let's take a simple case of, say, the "direction" class from the docs
(which has no default constructor) and try converting it to std::string.
Say, we want that conversion possible using a few converters with
std::sstream-based being one of them. In that setting I say #1 has the
following advantages (no matter how ugly I personally find it):
[...]
...
template
boost::optional<TypeOut>
...
basic_stringstream_converter::operator()(const TypeIn& in)
{
    boost::optional<TypeOut> out = boost::make_optional(boost::
convert_default_maker<TypeOut>::make());
stream_.str(std::basic_string< char_type>());
    stream_ << in; stream_ >> *out;
return out = stream_.fail() ? boost::optional<TypeOut> : out;
}
template
boost::optional<TypeOut>
lexical_cast_converter::operator()(const TypeIn& in)
{
try
    {
        boost::optional<TypeOut> out_value = boost::make_optional(boost::
convert_default_maker<TypeOut>::make());
        *out_value = boost::lexical_cast<TypeOut>(in);
        return out;
    }
    catch (...)
    {
        return out = boost::optional<TypeOut>;
    }
}
Why would you make a default TypeOut to then assign to it, instead of:

template
boost::optional<TypeOut>
lexical_cast_converter::operator()(const TypeIn& in)
{

    try
    {
        return boost::lexical_cast<TypeOut>(in);
    }
    catch (...)
    {
        return boost::none;
    }
}

Regards,
Kris

Re: [boost] Boost review of the Convert library is ongoing

Krzysztof Czainski