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
7 #include <boost/contract.hpp>
12 char replace(std::string& s, unsigned index, char x) {
14 boost::contract::old_ptr<char> old_char; // Null, old value copied later...
15 boost::contract::check c = boost::contract::function()
17 BOOST_CONTRACT_ASSERT(index < s.size());
19 .old([&] { // ...after preconditions (and invariants) checked.
20 old_char = BOOST_CONTRACT_OLDOF(s[index]);
23 BOOST_CONTRACT_ASSERT(s[index] == x);
24 BOOST_CONTRACT_ASSERT(result == *old_char);
35 std::string s = "abc";
36 char r = replace(s, 1, '_');