[boost] Suggestion to lexical_cast library

From: Márcio Gil (marciomgil_at_[hidden])
Date: 2007-12-15 17:53:49

Hello,

I suggest this add on lexical_cast library: a lexical_cast_def function,
which work's like the AnsiString's ToIntDef method (from Borland VCL).

Reason: the use of a lexical_cast without a try ... catch block, if the
source is not guaranteed to be safe. Example:

string source;
int x = lexical_cast_def<int>( source, 0 );

In opposite of:

string source;
int x;
try
{
  x = lexical_cast<int>( source );
}
catch(...)
{
  x = 0;
}

Soon I can write this function in my project:

    template<typename Target, typename Source>
    Target lexical_cast_def(Source arg, Target def)
    {
        Target result;
        try
        {
          result = lexical_cast<Target>(Source);
        }
        catch (..)
        {
          result = def;
        }
        return result;
    }

Otherwise we can post in the library this simplest and fastest function:
 
    template<typename Target, typename Source>
    Target lexical_cast_def(Source arg, Target def)
    {
        detail::lexical_stream<Target, Source> interpreter;
        Target result;

        if(!(interpreter << arg && interpreter >> result))
            return def;
        return result;
    }

And the call-by-const reference version.

Thanks,

Marcio Gil.

P.S.: This is my first post in this list, soon excuse my bad English, I
don't speak English, is that used only for reading.