boost.cpp

// #include <algorithm>
// #include <iostream>
// #include <iterator>

// #include <boost/lambda/lambda.hpp>

// int main() {
//   using namespace boost::lambda;
//   typedef std::istream_iterator<int> in;

//   std::for_each(
//     in(std::cin), in(),
//     std::cout << (_1 * 3) << " ");
// }

// #include <iostream>
// #include <string>

// #include <boost/regex.hpp>

// int main() {
//   std::string line;
//   boost::regex pat("^Subject: (Re: |Aw: )*(.*)");

//   while (std::cin) {
//     std::getline(std::cin, line);
//     boost::smatch matches;
//     if (boost::regex_match(line, matches, pat))
//       std::cout << matches[2] << std::endl;
//   }
// }

#include <iostream>

#include <boost/math/constants/constants.hpp>
#include <boost/multiprecision/cpp_dec_float.hpp>

using boost::multiprecision::cpp_dec_float_50;
using namespace std;

template<typename T>
inline T circle_area(T r) {
  // pi is predefined constant having value
  using boost::math::constants::pi;
  return pi<T>() * r * r;
}

int main() {
  float f_rad              = 243.0 / 100;
  float f_area             = circle_area(f_rad);
  double d_rad             = 243.0 / 100;
  double d_area            = circle_area(d_rad);
  cpp_dec_float_50 rad_mp  = 243.0 / 100;
  cpp_dec_float_50 area_mp = circle_area(rad_mp);

  cout << "Float: " << setprecision(numeric_limits<float>::digits10) << f_area << endl;

  // Double area
  cout << "Double: " << setprecision(numeric_limits<double>::digits10) << d_area << endl;

  // Area by using Boost Multiprecision
  cout << "Boost Multiprecision Res: " << setprecision(numeric_limits<cpp_dec_float_50>::digits10) << area_mp << endl;
  return 0;
}