Re: is it possible to get a unique key for a (instance, method) pair?

On Dec 5, 5:50 am, t.lehm...@rtsgroup.net wrote:


You might try:

  template<typename X> struct MethodComparator {
    union Transfer {
      SIMPLE_METHOD m;
      char bytes[sizeof(SIMPLE_METHOD)];
    }; // Used because reinterpret_cast<char*>(memfun_ptr) is illegal.
    bool operator()(const KEY_METHOD& lhs, const KEY_METHOD& rhs) {
      if (lhs.first < rhs.first) return true;
      if (rhs.first < lhs.first) return false;
      // Important lines:
      Transfer lhs_method;
      lhs_method.m = lhs.second;
      Transfer rhs_method;
      rhs_method.m = rhs.second;
      return lexicographical_compare(lhs_method.bytes, lhs_method.bytes
+ sizeof(lhs_method.bytes),
                                     rhs_method.bytes, rhs_method.bytes
+ sizeof(rhs_method.bytes));
    }
  };

  typedef std::map<KEY_METHOD, WrapperBase*, MethodComparator>
METHOD_MAP;

Here I'm comparing the bit patterns of the two method pointers. This is
undefined according to the standard, but I suspect that many or most
compilers do the Right Thing.

Jeffrey

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