Re: [Boost-users] lexical_cast and infinity

From: Ben Hutchings (ben.hutchings_at_[hidden])
Date: 2005-03-29 06:50:02

Patrick Mézard wrote:
> The last line of the following program throws a bad_lexical_cast exception. The
> code is compiled with VC7.1.
> 
> //**********************************************************
> #include <limits>
> #include <iostream>
> #include <boost/lexical_cast.hpp>
> 
> int main(int argc, char* argv[])
> {
>     double d = std::numeric_limits<double>::infinity();
>     std::string s = boost::lexical_cast<std::string>(d);
>     std::cout<<d<<", "<<s<<std::endl;
> 
>     //Throws bad_lexical_cast
>     boost::lexical_cast<double>(s);
> }
> //**********************************************************
> 
> The output is:
> 
> "1.#INF, 1.#INF"
> 
> Am I doing something wrong ?

Textual representations of infinities and NaNs are not specified in the 
C++ standard or the C90 standard which it references (though they are in 
C99).  So there is unfortunately no guarantee that you can successfully 
convert them to and from strings.

Ben.