2012/4/11 Eric Niebler <eric@boostpro.com>:
There is an internal trait, boost::detail::stream_char, that lexical_cast uses to determine what the character type of the source is (if any). It's specialized on only a fixed number of types. Since it's an implementation detail, it can't be used to extend the set of types. Also, I tried specializing it. In past versions of Boost that just worked, but it doesn't anymore.
I think being able to extend lexical_cast to support types like (std|boost)::wssub_match is an essential feature. Thoughts on how to get there from here?
Specializing boost::detail::stream_char is not nice. Why just you don't specialize lexical_cast directly: namespace boost { template <class Target, class BiIter> Target lexical_cast(const sub_match<BiIter>& m) { return boost::lexical_cast<Target>(m.str()); } } // namespace boost [Not tested] Using this approach you will also get a faster version of lexical_cast (which does not copy data to STL stream and does not construct heavy STL stream objects). This approach is also described in lexical_cast trunk documentation, in section 'Tuning classes for fast lexical conversions'. I'll add your question to the FAQ section of lexical_cast documentation. -- Best regards, Antony Polukhin