gistfile1.txt

template<typename Data, typename Function>
struct function_object_adaptor {
 public:
  typedef typename Function::result_type value_type;
  typedef value_type& reference;
  typedef value_type* pointer;

 private:
  Data data;
  Function f;

  // shared Assignable implementation
  void copy (function_object_adaptor const& x) {
    data = x.data;
    f = f.data;
  }

 public:
  // STL DefaultConstructible
  function_object_adaptor (Data d_ = Data(), Function f_ = Function()):
    data(d_), f(f_)
  {
    f(data); // call f on data
  }

  // STL Assignable
  function_object_adaptor (function_object_adaptor const& x) {
    copy(x);
  }

  // STL EqualityComparable 
  bool operator== (function_object_adaptor const& rhs) {
    return (data == rhs.data)
        && (f == rhs.f);
  }
  
  // STL EqualityComparable 
  bool operator!= (function_object_adaptor const& rhs) {
    return (data != rhs.data)
        && (f != rhs.f);
  }

  // STL Assignable
  function_object_adaptor& operator= (function_object_adaptor const& x) {
    if (*this != x) copy(x);
    return *this;
  }

  // STL TrivialIterator   
  reference operator* (void) const {
    return f.get();
  }

  // STL TrivialIterator   
  pointer operator-> (void) const {
    return f.ptr();
  }

  // STL ForwardIterator
  function_object_adaptor& operator++ (void) {
    f(++data); return *this;
  }

  // STL ForwardIterator
  function_object_adaptor operator++ (int) {
    function_object_adaptor tmp = *this;
    return ++tmp;
  }

  bool at (Data const& d_) const {
    return data == d_;
  }
};