There has been some discussion about a minor improvement to lexical_cast to
ensure that a loopback test like:
any_type any_value == lexical_cast<T>(lexical_cast<string>(any_value))
is always true
The following replacement for the original code (using digits10+1) works for
specialised radix 2 types:
if(std::numeric_limits<Target>::is_specialized
&& std::numeric_limits<Target>::radix == 2)
{
stream.precision(2 + std::numeric_limits<Target>::digits * 301/1000);
}
else if(std::numeric_limits<Source>::is_specialized
&& std::numeric_limits<Source>::radix == 2)
{
stream.precision(2 + std::numeric_limits<Source>::digits * 301/1000);
}
As in the current version, for other types the default precision is used, and
you may not get what you expect. I think this is OK, but one could throw an
exception. I propose a comment instead
// Warning: else the default stream precision (usually 6) will be used,
// which may not be enough significant decimal digits to avoid losing precision,
// for example in a loopback test like
// some_type any_value == lexical_cast<T>(lexical_cast<string>(any_value));
If there are no objections, can someone with sufficient authority patch
lexical_cast.hpp?
Paul
Paul A Bristow, Prizet Farmhouse, Kendal, Cumbria, LA8 8AB UK
+44 1539 561830 Mobile +44 7714 33 02 04
mailto:[EMAIL PROTECTED]
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