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// 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 <boost/config.hpp>
#include <cassert>
#ifdef BOOST_GCC // G++ does not support static union members yet.
int instances_ = 0;
#endif
//[union
union positive {
public:
static void static_invariant() { // Static class invariants (as usual).
BOOST_CONTRACT_ASSERT(instances() >= 0);
}
void invariant() const { // Class invariants (as usual).
BOOST_CONTRACT_ASSERT(i_ > 0);
BOOST_CONTRACT_ASSERT(d_ > 0);
}
// Contracts for constructor, as usual but...
explicit positive(int x) : d_(0) {
// ...unions cannot have bases so constructor preconditions here.
boost::contract::constructor_precondition<positive> pre([&] {
BOOST_CONTRACT_ASSERT(x > 0);
});
boost::contract::old_ptr<int> old_instances =
BOOST_CONTRACT_OLDOF(instances());
boost::contract::check c = boost::contract::constructor(this)
.postcondition([&] {
{ int y; get(y); BOOST_CONTRACT_ASSERT(y == x); }
BOOST_CONTRACT_ASSERT(instances() == *old_instances + 1);
})
;
i_ = x;
++instances_;
}
// Contracts for destructor (as usual).
~positive() {
boost::contract::old_ptr<int> old_instances =
BOOST_CONTRACT_OLDOF(instances());
boost::contract::check c = boost::contract::destructor(this)
.postcondition([&] {
BOOST_CONTRACT_ASSERT(instances() == *old_instances - 1);
})
;
--instances_;
}
// Contracts for public function (as usual, but no virtual or override).
void get(int& x) const {
boost::contract::check c = boost::contract::public_function(this)
.postcondition([&] {
BOOST_CONTRACT_ASSERT(x > 0);
})
;
x = i_;
}
// Contracts for static public function (as usual).
static int instances() {
boost::contract::check c = boost::contract::public_function<positive>();
return instances_;
}
private:
int i_;
double d_;
/* ... */
//]
public:
explicit positive(double x) : d_(0) {
// Unions cannot have bases so constructor preconditions here.
boost::contract::constructor_precondition<positive> pre([&] {
BOOST_CONTRACT_ASSERT(x > 0);
});
boost::contract::old_ptr<int> old_instances =
BOOST_CONTRACT_OLDOF(instances());
boost::contract::check c = boost::contract::constructor(this)
.postcondition([&] {
{ double y; get(y); BOOST_CONTRACT_ASSERT(y == x); }
BOOST_CONTRACT_ASSERT(instances() == *old_instances + 1);
})
;
d_ = x;
++instances_;
}
void get(double& x) const {
boost::contract::check c = boost::contract::public_function(this)
.postcondition([&] {
BOOST_CONTRACT_ASSERT(x > 0);
})
;
x = d_;
}
#ifndef BOOST_GCC // G++ does not support static union members yet.
static int instances_;
#endif
};
#ifndef BOOST_GCC // G++ does not support static union members yet.
int positive::instances_ = 0;
#endif
int main() {
{
positive p(123);
assert(p.instances() == 1);
{ int y = -456; p.get(y); assert(y == 123); }
positive q(1.23);
assert(q.instances() == 2);
{ double y = -4.56; q.get(y); assert(y == 1.23); }
}
assert(positive::instances() == 0);
return 0;
}
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