Method to_string

include/chaiscript/utility/json.hpp:326–326

    bool is_null() const { return internal.Type == Class::Null; }

    std::string to_string() const { bool b; return to_string( b ); }
    std::string to_string( bool &ok ) const {
      ok = (internal.Type == Class::String);
      return ok ? *internal.String : std::string("");