traits.cpp

#include <iostream>

  inline bool IsNull( const std::string& v ) { return ( v == "" ); }
  inline bool IsNull( long  v ) { return ( v == 0 ); }
  inline bool IsNull( char c ) { return ( c == 0 ); }

template <typename T>
  bool IsNotNull(const T & v) { return !IsNull(v); }


template <typename T>
struct Traits
{
  typedef const T& param_type;
};

template <>
struct Traits<int>
{
  typedef int param_type;
};

int main()
{
  f(2);
  int a = 3;
  f(a);
  
}