/*
 * function-objects-02.cc    Standard Library, Funtion objects, exercise 2.
 */
#include <algorithm>
#include <functional>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>
using namespace std;
using namespace std::placeholders;

template<typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
   copy(begin(v), end(v), ostream_iterator<T>(os, " "));
   return os;
}

template<typename T, T value_>
struct greater_than
{
   bool operator()(const T& value) const 
   {
      return value_ < value;
   }

   typedef bool result_type;
   typedef T    argument_type;
};

template<typename T, T value_>
struct not_equal
{
   bool operator()(const T& value) const
   {
      return !(value_ == value);  // if != not present
   }

   typedef bool result_type;
   typedef T    argument_type;
};

template<typename T, T factor_>
struct multiply_by
{
   T operator()(const T& value) const
   {
      return factor_ * value;
   }

   typedef T result_type;
   typedef T argument_type;
};

int main()
{
   vector<int> v{ 5, 4, 12, 8, 2, 1, 3, 10, 9, 7, 6, 11 };
   cout << "\nValues in the vector:\n" << v << "\n\n";

   ostream_iterator<int> out(cout, " ");

   // a)
   cout << "Values in the vector greater than 5:\n";
   copy_if(begin(v), end(v), out, ::greater_than<int, 5>());
   cout << "\n\n";

   cout << "Values in the vector greater than 5 (only std):\n";
   remove_copy_if(begin(v), end(v), out, bind(less_equal<int>(), _1, 5));
   cout << "\n\n";
   // b)
   cout << "Values in the vector not equal to 10:\n";
   copy_if(begin(v), end(v), out, not_equal<int, 10>());
   cout << "\n\n";

   cout << "Values in the vector not equal to 10 (only std):\n";
   copy_if(begin(v), end(v), out, bind(not_equal_to<int>(), 10, _1));
   cout << "\n\n";
   // c)
   cout << "Multiply each value in the vector by 2:\n";
   transform(begin(v), end(v), begin(v), multiply_by<int, 2>());
   cout << v << "\n\n";

   cout << "Multiply each value in the vector by 2 again (only std):\n";
   transform(begin(v), end(v), begin(v), 
	     bind(multiplies<int>(), _1, 2));
   cout << v << "\n\n";
}