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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
//[meyer97_stack3
// File: stack3.cpp
#include "stack4.hpp"
#include <boost/contract.hpp>
#include <boost/optional.hpp>
#include <cassert>
// Dispenser LIFO with max capacity using error codes.
template<typename T>
class stack3 {
friend class boost::contract::access;
void invariant() const {
if(!error()) {
BOOST_CONTRACT_ASSERT(count() >= 0); // Count non-negative.
BOOST_CONTRACT_ASSERT(count() <= capacity()); // Count bounded.
// Empty if no element.
BOOST_CONTRACT_ASSERT(empty() == (count() == 0));
}
}
public:
enum error_code {
no_error = 0,
overflow_error,
underflow_error,
size_error
};
/* Initialization */
// Create stack for max of n elems, if n < 0 set error (no preconditions).
explicit stack3(int n, T const& default_value = T()) :
stack_(0), error_(no_error) {
boost::contract::check c = boost::contract::constructor(this)
.postcondition([&] {
// Error if impossible.
BOOST_CONTRACT_ASSERT((n < 0) == (error() == size_error));
// No error if possible.
BOOST_CONTRACT_ASSERT((n >= 0) == !error());
// Created if no error.
if(!error()) BOOST_CONTRACT_ASSERT(capacity() == n);
})
;
if(n >= 0) stack_ = stack4<T>(n);
else error_ = size_error;
}
/* Access */
// Max number of stack elements.
int capacity() const {
// Check invariants.
boost::contract::check c = boost::contract::public_function(this);
return stack_.capacity();
}
// Number of stack elements.
int count() const {
// Check invariants.
boost::contract::check c = boost::contract::public_function(this);
return stack_.count();
}
// Top element if present, otherwise none and set error (no preconditions).
boost::optional<T const&> item() const {
boost::contract::check c = boost::contract::public_function(this)
.postcondition([&] {
// Error if impossible.
BOOST_CONTRACT_ASSERT(empty() == (error() == underflow_error));
// No error if possible.
BOOST_CONTRACT_ASSERT(!empty() == !error());
})
;
if(!empty()) {
error_ = no_error;
return boost::optional<T const&>(stack_.item());
} else {
error_ = underflow_error;
return boost::optional<T const&>();
}
}
/* Status Report */
// Error indicator set by various operations.
error_code error() const {
// Check invariants.
boost::contract::check c = boost::contract::public_function(this);
return error_;
}
bool empty() const {
// Check invariants.
boost::contract::check c = boost::contract::public_function(this);
return stack_.empty();
}
bool full() const {
// Check invariants.
boost::contract::check c = boost::contract::public_function(this);
return stack_.full();
}
/* Element Change */
// Add x to top if capacity allows, otherwise set error (no preconditions).
void put(T const& x) {
boost::contract::old_ptr<bool> old_full = BOOST_CONTRACT_OLDOF(full());
boost::contract::old_ptr<int> old_count = BOOST_CONTRACT_OLDOF(count());
boost::contract::check c = boost::contract::public_function(this)
.postcondition([&] {
// Error if impossible.
BOOST_CONTRACT_ASSERT(*old_full == (error() == overflow_error));
// No error if possible.
BOOST_CONTRACT_ASSERT(!*old_full == !error());
if(!error()) { // If no error...
BOOST_CONTRACT_ASSERT(!empty()); // ...not empty.
BOOST_CONTRACT_ASSERT(*item() == x); // ...added to top.
// ...one more.
BOOST_CONTRACT_ASSERT(count() == *old_count + 1);
}
})
;
if(full()) error_ = overflow_error;
else {
stack_.put(x);
error_ = no_error;
}
}
// Remove top element if possible, otherwise set error (no preconditions).
void remove() {
boost::contract::old_ptr<bool> old_empty =
BOOST_CONTRACT_OLDOF(empty());
boost::contract::old_ptr<int> old_count = BOOST_CONTRACT_OLDOF(count());
boost::contract::check c = boost::contract::public_function(this)
.postcondition([&] {
// Error if impossible.
BOOST_CONTRACT_ASSERT(*old_empty == (error() ==
underflow_error));
// No error if possible.
BOOST_CONTRACT_ASSERT(!*old_empty == !error());
if(!error()) { // If no error...
BOOST_CONTRACT_ASSERT(!full()); // ...not full.
// ...one less.
BOOST_CONTRACT_ASSERT(count() == *old_count - 1);
}
})
;
if(empty()) error_ = underflow_error;
else {
stack_.remove();
error_ = no_error;
}
}
private:
stack4<T> stack_;
mutable error_code error_;
};
int main() {
stack3<int> s(3);
assert(s.capacity() == 3);
assert(s.count() == 0);
assert(s.empty());
assert(!s.full());
s.put(123);
assert(!s.empty());
assert(!s.full());
assert(*s.item() == 123);
s.remove();
assert(s.empty());
assert(!s.full());
return 0;
}
//]
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