Re: Howto identify a string value vs. a numeric value in std::string

frohlinger@gmail.com wrote:


#include <sstream>
#include <iostream>
#include <typeinfo> // bad_cast

template <class To, class From>
To LexicalCast(From const& from)
{
     std::ostringstream oss;
     oss << from;
     if (!oss)
         throw std::bad_cast("Lexical cast error");

     std::istringstream iss(oss.str());
     To to;
     iss >> to;
     if (!(iss && iss.get() == std::char_traits<char>::eof()))
         throw std::bad_cast("Lexical cast error");

     return to;
}

int main(int argc, char* argv[])
{
     try {
         int i = LexicalCast<int>(argc == 1 ? "1234" : argv[1]);
         std::cout << i << std::endl;
     }
     catch (std::bad_cast const& ex) {
         std::cerr<< ex.what() << std::endl;
     }
}

if you don't like stringstream way

you can do some extra check (like using strspn), then do the casting

--
Thanks
Barry