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130 lines
3.6 KiB
C++
130 lines
3.6 KiB
C++
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//[mitchell02_name_list
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#include <boost/contract.hpp>
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#include <boost/detail/lightweight_test.hpp>
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#include <string>
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#include <vector>
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#include <algorithm>
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// List of names.
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class name_list {
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public:
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void invariant() const {
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BOOST_CONTRACT_ASSERT(count() >= 0); // Non-negative count.
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}
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/* Creation */
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// Create an empty list.
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name_list() {
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auto c = boost::contract::constructor(this)
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.postcondition([&] {
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BOOST_CONTRACT_ASSERT(count() == 0); // Empty list.
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})
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;
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}
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// Destroy list.
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virtual ~name_list() {
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auto c = boost::contract::destructor(this); // Check invariants.
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}
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/* Basic Queries */
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// Number of names in list.
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int count() const {
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auto c = boost::contract::public_function(this); // Check invariants.
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return names_.size();
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}
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// Is name in list?
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bool has(std::string const& name) const {
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bool result;
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auto c = boost::contract::public_function(this)
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.postcondition([&] {
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// If empty, has not.
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if(count() == 0) BOOST_CONTRACT_ASSERT(!result);
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})
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;
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return result = names_.cend() != std::find(names_.cbegin(),
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names_.cend(), name);
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}
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/* Commands */
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// Add name to list, if name not already in list.
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virtual void put(std::string const& name,
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boost::contract::virtual_* v = 0) {
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auto old_has_name = BOOST_CONTRACT_OLDOF(v, has(name));
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auto old_count = BOOST_CONTRACT_OLDOF(v, count());
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auto c = boost::contract::public_function(v, this)
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.precondition([&] {
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BOOST_CONTRACT_ASSERT(!has(name)); // Not already in list.
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})
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.postcondition([&] {
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if(!*old_has_name) { // If-guard allows to relax subcontracts.
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BOOST_CONTRACT_ASSERT(has(name)); // Name in list.
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BOOST_CONTRACT_ASSERT(count() == *old_count + 1); // Inc.
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}
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})
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;
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names_.push_back(name);
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}
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private:
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std::vector<std::string> names_;
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};
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class relaxed_name_list
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#define BASES public name_list
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: BASES
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{
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public:
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typedef BOOST_CONTRACT_BASE_TYPES(BASES) base_types; // Subcontracting.
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#undef BASES
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/* Commands */
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// Add name to list, or do nothing if name already in list (relaxed).
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void put(std::string const& name,
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boost::contract::virtual_* v = 0) /* override */ {
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auto old_has_name = BOOST_CONTRACT_OLDOF(v, has(name));
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auto old_count = BOOST_CONTRACT_OLDOF(v, count());
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auto c = boost::contract::public_function<override_put>(
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v, &relaxed_name_list::put, this, name)
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.precondition([&] { // Relax inherited preconditions.
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BOOST_CONTRACT_ASSERT(has(name)); // Already in list.
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})
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.postcondition([&] { // Inherited post. not checked given if-guard.
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if(*old_has_name) {
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// Count unchanged if name already in list.
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BOOST_CONTRACT_ASSERT(count() == *old_count);
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}
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})
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;
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if(!has(name)) name_list::put(name); // Else, do nothing.
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}
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BOOST_CONTRACT_OVERRIDE(put);
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};
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int main() {
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std::string const js = "John Smith";
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relaxed_name_list rl;
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rl.put(js);
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BOOST_TEST(rl.has(js));
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rl.put(js); // OK, relaxed contracts allow calling this again (do nothing).
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name_list nl;
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nl.put(js);
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BOOST_TEST(nl.has(js));
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// nl.put(js); // Error, contracts do not allow calling this again.
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return boost::report_errors();
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}
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//]
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