C++ traits to know if a type has a method.

gistfile1.c++

#include <iostream>
#include <vector>
#include <list>
#include <set>

template <typename T>
struct HasPushBack {
  typedef char yes[1];
  typedef char no[2];

  template <class U, void (U::*)(const typename U::value_type &) = &U::push_back> struct MethodTraits;

  template <typename U>
  static yes& _has(MethodTraits<U>*);

  template <typename>
  static no& _has(...);

  static const bool value = sizeof (_has<T>(0)) == sizeof (yes);
};

int main() {
  std::clog << HasPushBack<int>::value << std::endl;
  std::clog << HasPushBack<std::vector<int> >::value << std::endl;
  std::clog << HasPushBack<std::list<int> >::value << std::endl;
  std::clog << HasPushBack<std::set<int> >::value << std::endl;
}