ceph/src/boost/libs/safe_numerics/example/example15.cpp

   1 //  Copyright (c) 2018 Robert Ramey
   2 //
   3 // Distributed under the Boost Software License, Version 1.0. (See
   4 // accompanying file LICENSE_1_0.txt or copy at
   5 // http://www.boost.org/LICENSE_1_0.txt)
   6
   7 #include <iostream>
   8 #include <limits>
   9
  10 #include <boost/rational.hpp>
  11 #include <boost/safe_numerics/safe_integer.hpp>
  12
  13 int main(int, const char *[]){
  14     // simple demo of rational library
  15     const boost::rational<int> r {1, 2};
  16     std::cout << "r = " << r << std::endl;
  17     const boost::rational<int> q {-2, 4};
  18     std::cout << "q = " << q << std::endl;
  19     // display the product
  20     std::cout << "r * q = " << r * q << std::endl;
  21
  22     // problem: rational doesn't handle integer overflow well
  23     const boost::rational<int> c {1, INT_MAX};
  24     std::cout << "c = " << c << std::endl;
  25     const boost::rational<int> d {1, 2};
  26     std::cout << "d = " << d << std::endl;
  27     // display the product - wrong answer
  28     std::cout << "c * d = " << c * d << std::endl;
  29
  30     // solution: use safe integer in rational definition
  31     using safe_rational = boost::rational<
  32         boost::safe_numerics::safe<int>
  33     >;
  34
  35     // use rationals created with safe_t
  36     const safe_rational sc {1, std::numeric_limits<int>::max()};
  37
  38     std::cout << "c = " << sc << std::endl;
  39     const safe_rational sd {1, 2};
  40     std::cout << "d = " << sd << std::endl;
  41     std::cout << "c * d = ";
  42     try {
  43         // multiply them. This will overflow
  44         std::cout << (sc * sd) << std::endl;
  45     }
  46     catch (std::exception const& e) {
  47         // catch exception due to multiplication overflow
  48         std::cout << e.what() << std::endl;
  49     }
  50
  51     return 0;
  52 }