blob: bdf8b8c6e6fdd6b43714433b463930fb17ab9d45 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
|
// Copyright (C) 2008-2018 Lorenzo Caminiti
// Distributed under the Boost Software License, Version 1.0 (see accompanying
// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
#include <boost/contract.hpp>
#include <string>
#include <cassert>
//[old
char replace(std::string& s, unsigned index, char x) {
char result;
boost::contract::old_ptr<char> old_char; // Null, old value copied later...
boost::contract::check c = boost::contract::function()
.precondition([&] {
BOOST_CONTRACT_ASSERT(index < s.size());
})
.old([&] { // ...after preconditions (and invariants) checked.
old_char = BOOST_CONTRACT_OLDOF(s[index]);
})
.postcondition([&] {
BOOST_CONTRACT_ASSERT(s[index] == x);
BOOST_CONTRACT_ASSERT(result == *old_char);
})
;
result = s[index];
s[index] = x;
return result;
}
//]
int main() {
std::string s = "abc";
char r = replace(s, 1, '_');
assert(s == "a_c");
assert(r == 'b');
return 0;
}
|
