// This example demonstrates how to use 'reduce' method.

#include 

#include 
#include 

struct Data {
  int a {::rand()};
  int b {::rand()};
  int transform() const { 
    return a*a + 2*a*b + b*b;
  }
};

// Procedure: reduce
// This procedure demonstrates 
void reduce() {
  
  std::cout