How to get information about “current type” inside of a struct/class?

Question

Is it possible to get "type of the current struct " inside of the struct ? For example, I want to do something like this:

struct foobar {
  int x, y;

  bool operator==(const THIS_TYPE& other) const  /*  What should I put here instead of THIS_TYPE? */
  {
    return x==other.x && y==other.y;
  }
}

I tried to do it this way:

struct foobar {
  int x, y;

  template<typename T>
  bool operator==(const T& t) const
  {
    decltype (*this)& other = t; /* We can use `this` here, so we can get "current type"*/
    return x==other.x && y==other.y;
  }
}

but it looks ugly, requires support of the latest C++ Standard, and MSVC connot compile it (it crashes with "an internal error").

Actually, I just want to write some preprocessor macros to auto-generate functions like operator== :

struct foobar {
  int x, y;
  GEN_COMPARE_FUNC(x, y);
}

struct some_info {
  double len;
  double age;
  int rank;
  GEN_COMPARE_FUNC(len, age, rank);
}

But I need to know "current type" inside of the macro.

Answer 1

Actually, you can use somethink like this.

#define GEN_COMPARE_FUNC(type, x, y)\
template<typename type>\
bool operator ==(const type& t) const\
{\
    return this->x == t.x && this->y == t.y;\
}

struct Foo
{
    int x, y;
    GEN_COMPARE_FUNC(Foo, x, y);
};

I have no idea, how use var. macro-pars in this way (we need to go throw the params and compare each par from this and from t, i have no idea, how expand params in macro).

Answer 2

This stack-overflow URL states that the boost libraries can compute the type of an expression, but C/C++ by itself cannot:

Getting name and type of a struct field from its object

Someone asked a similar question also:

How can I add reflection to a C++ application?

To start using typeof include the typeof header:

#include <boost/typeof/typeof.hpp>

To deduce the type of an expression at compile time use the BOOST_TYPEOF macro:

namespace ex1
{
    typedef BOOST_TYPEOF(1 + 0.5) type;

    BOOST_STATIC_ASSERT((is_same<type, double>::value));
}