Re: [Boost-users] Template instantiation problem

11 May 2006


      Have you looked at boost::variant?
You can use operator<< and ostringstream to convert to string.

Use something this:
#include 
#include <string>
#include <iostream>
#include <sstream>

typedef boost::variant my_variant;

int main()
{
  unsigned char u2 = 2;
  my_variant mv1(u2);
  int i2 = 2;
  my_variant mv2(i2);
  my_variant mv3(std::string("3"));

  std::ostringstream oss (std::ostringstream::out);

  oss << mv1;
  std::cout << oss.str();
  oss << mv2;
  std::cout << oss.str();
  oss << mv3;
  std::cout << oss.str();
}

Chris

On 5/10/06, Rush Manbert  wrote:
...
I have a template class that is designed to contain built in types or
std::string types. I always need to be able to cast an instance of the
class as a std::string, and I also need to be able to cast it as the
parameter type with which it was instantiated.
In my class definition, I have defined two cast operators, like so:
(Extraneous stuff omitted)
template<typename T>
class MyDataObject : public MyDataObjectBase
{
// Cast as std::string
        inline                  operator const std::string &    ()
                                {
                                        ...some code here
                                }
// Cast as T
        inline                  operator const T &              ()
                                {
                                        ...some code here
                                }
}
The original code was written on a Mac and compiled with Gnu, which did
not complain. even when I did this:
class MyStringObjectClass : public MyDataObjectstd::string
{
}
Now, however, I have moved the code to Windows, and the Visual Studio
compiler complains about the second cast operator when I define
MyStringObjectClass.
I thought that if I could conditionally define the cast as T operator
(or the cast as std::string) I would be okay, but that means testing
against the value of T with the preprocessor. I don't see how to do
that, but I know that some of you folks are really good at bending the
preprocessor to your will.
Can anyone show me a way out of this predicament?
Thanks,
Rush
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Re: [Boost-users] Template instantiation problem

Chris Weed