ceph/src/boost/libs/contract/example/features/old.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 #include <boost/contract.hpp>
   8 #include <string>
   9 #include <cassert>
  10
  11 //[old
  12 char replace(std::string& s, unsigned index, char x) {
  13     char result;
  14     boost::contract::old_ptr<char> old_y; // Null, old value copied later...
  15     boost::contract::check c = boost::contract::function()
  16         .precondition([&] {
  17             BOOST_CONTRACT_ASSERT(index < s.size());
  18         })
  19         .old([&] { // ...after preconditions (and invariants) checked.
  20             old_y = BOOST_CONTRACT_OLDOF(s[index]);
  21         })
  22         .postcondition([&] {
  23             BOOST_CONTRACT_ASSERT(s[index] == x);
  24             BOOST_CONTRACT_ASSERT(result == *old_y);
  25         })
  26     ;
  27
  28     result = s[index];
  29     s[index] = x;
  30     return result;
  31 }
  32 //]
  33
  34 int main() {
  35     std::string s = "abc";
  36     char r = replace(s, 1, '_');
  37     assert(s == "a_c");
  38     assert(r == 'b');
  39     return 0;
  40 }
  41