C++ Operator Overload addition operator for Pool objects with this pointer

#include <iostream>
#include <vector>
#include <cstdlib>                     // For random number generator
#include <ctime>                       // For time function
#include <iostream>
#include <iomanip>

class  Pool/*  www.java  2s. c om*/
{
private:
  double length {1.0};
  double width {1.0};
  double height {1.0};

public:
  // Constructors
  Pool(double lv, double wv, double hv) : length {lv}, width {wv}, height {hv} {}

  Pool() {}                                                             // No-arg constructor

  Pool(const Pool& pool)                                                  // Copy constructor
    : length {pool.length}, width {pool.width}, height {pool.height} {}

  double volume() const                                                // Function to calculate the volume
  {
    return length*width*height;
  }

  // Accessors
  double getLength() const { return length; }
  double getWidth() const { return width; }
  double getHeight() const { return height; }

  bool operator<(const Pool& aPool) const;                               // Less-than operator
  bool operator<(double aValue) const;                                 // Compare Pool volume < double value
  Pool operator+(const Pool& aPool) const;                                // Function to add two Pool objects

  void listPool();                                                      // Output the Pool
};

// Less-than comparison for Pool objects
inline bool Pool::operator<(const Pool& aPool) const
{
  return volume() < aPool.volume();
}

// Compare the volume of a Pool object with a constant
inline bool Pool::operator<(double aValue) const
{
  return volume() < aValue;
}

// Function comparing a constant with volume of a Pool object
inline bool operator<(double aValue, const Pool& aPool)
{
  return aValue < aPool.volume();
}

// Operator function to add two Pool objects
inline Pool Pool::operator+(const Pool& aPool) const
{
  // New object has larger length and width, and sum of heights
  return Pool {length > aPool.length ? length : aPool.length,
    width > aPool.width ? width : aPool.width,
    height + aPool.height};
}

// Output the Pool
inline void Pool::listPool()
{
  std::cout << " Pool(" << std::setw(2) << length << ","
    << std::setw(2) << width << ","
    << std::setw(2) << height << ")";
}

// Stream output for Pool objects
std::ostream& operator<<(std::ostream& stream, const Pool& pool)
{
  stream << " Pool(" << std::setw(2) << pool.getLength() << ","
    << std::setw(2) << pool.getWidth() << ","
    << std::setw(2) << pool.getHeight() << ")";
  return stream;
}

// Function to generate integral random pool dimensions from 1 to max_size
inline double random(double max_size)
{
  return 1 + static_cast<int>(max_size* static_cast<double>(std::rand()) / (RAND_MAX + 1.0));
}

int main()
{
  const double dimLimit {99.0};        // Upper limit on Pool dimensions
  std::srand((unsigned) std::time(0));  // Initialize the random number generator

  const int poolCount {20};          // Number of Pool object to be created
  std::vector<Pool> pools;              // Vector of Pool objects

  // Create 20 Pool objects
  for (int i {}; i < poolCount; ++i)
    pools.push_back(Pool {random(dimLimit), random(dimLimit), random(dimLimit)});

  int first {};                      // Index of first Pool object of pair
  int second {1};                    // Index of second Pool object of pair
  double minVolume {(pools[first] + pools[second]).volume()};

  for (int i {}; i < poolCount - 1; ++i)
    for (int j {i + 1}; j < poolCount; j++)
      if (pools[i] + pools[j] < minVolume)
      {
        first = i;
        second = j;
        minVolume = (pools[i] + pools[j]).volume();
      }

  std::cout << "The two pools that sum to the smallest volume are: "
            << pools[first] << pools[second];
  std::cout << "\nThe volume of the first pool is " << pools[first].volume();
  std::cout << "\nThe volume of the second pool is " << pools[second].volume();
  std::cout << "\nThe pool that the sum of these pools is" << pools[first] + pools[second];
  std::cout << "\nThe volume of the sum is " << minVolume << std::endl;
}