In writing some unit tests to convert strings to floats I've come across a puzzling situation. I was trying to test that a std::bad_cast was thrown if a number was too large to fit into a float. The error wasn't thrown but the float was given 1.#INF000. The work around I used was to cast to a double and then do a numeric_cast on the result. This provided an exception for values larger than could fit in a float. Lexical_cast on a double though works as I would have expected. If a value is too large to fit into a double then a std::bad_cast is called. float test = boost::lexical_cast<float>("3.4e050"); //test will have the value of 1.#INF000 float test = boost::numeric_cast<float>( boost::lexical_cast<double>("3.4e50"); //std::bad_cast is thrown double test = boost::lexical_cast<double>("3.4e350"); //std::bad_cast is thrown Is the lexical_cast for float behaving correctly? Ryan P.S. This code is using boost 1.38.0