ceph/src/boost/libs/contract/example/n1962/equal.cpp

   1
   2 // Copyright (C) 2008-2018 Lorenzo Caminiti
   3 // Distributed under the Boost Software License, Version 1.0 (see accompanying
   4 // file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
   5 // See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
   6
   7 //[n1962_equal
   8 #include <boost/contract.hpp>
   9 #include <cassert>
  10
  11 // Forward declaration because == and != contracts use one another's function.
  12 template<typename T>
  13 bool operator==(T const& left, T const& right);
  14
  15 template<typename T>
  16 bool operator!=(T const& left, T const& right) {
  17     bool result;
  18     boost::contract::check c = boost::contract::function()
  19         .postcondition([&] {
  20             BOOST_CONTRACT_ASSERT(result == !(left == right));
  21         })
  22     ;
  23
  24     return result = (left.value != right.value);
  25 }
  26
  27 template<typename T>
  28 bool operator==(T const& left, T const& right) {
  29     bool result;
  30     boost::contract::check c = boost::contract::function()
  31         .postcondition([&] {
  32             BOOST_CONTRACT_ASSERT(result == !(left != right));
  33         })
  34     ;
  35
  36     return result = (left.value == right.value);
  37 }
  38
  39 struct number { int value; };
  40
  41 int main() {
  42     number n;
  43     n.value = 123;
  44
  45     assert((n == n) == true);   // Explicitly call operator==.
  46     assert((n != n) == false);  // Explicitly call operator!=.
  47
  48     return 0;
  49 }
  50 //]
  51