[boost] [lexical_cast] bug in T -> string ? Re: [serialization] Serialisation/deserialisationoffloating-point values

From: Kevin Wheatley (hxpro_at_[hidden])
Date: 2006-03-16 04:21:51

Caleb Epstein wrote:
> Note that boost::lexical_cast uses a precision of
> std::numeric_limits<T>::digits10
> + 1 in its T-to-string conversions.  For double, this is 16 which would
> probably explain the mismatch on the 17th significant digit on two separate
> platforms.

so it looks like lexical_cast has a bug (repeated) as well then see
Paul Bristow's comment earlier, here is the code in lexical_cast.hpp.

            lexical_stream()
            {
                stream.unsetf(std::ios::skipws);

                if(std::numeric_limits<Target>::is_specialized)
                   
stream.precision(std::numeric_limits<Target>::digits10 + 1);
                else if(std::numeric_limits<Source>::is_specialized)
                   
stream.precision(std::numeric_limits<Source>::digits10 + 1);
            }

Should both be tweaked to add the extra digits:

stream.precision(2+std::numeric_limits<Target>::digits * 3010/10000);

and

stream.precision(2+std::numeric_limits<Source>::digits * 3010/10000);

or am I missing the boat on my quick inspection

Kevin

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