lean2/src/util/scoped_set.h

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/*
Copyright (c) 2013 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Author: Leonardo de Moura
*/
#pragma once
#include <unordered_set>
#include <vector>
#include <utility>
#include <functional>
#include "util/debug.h"
#include "util/pair.h"
#ifndef LEAN_SCOPED_SET_INITIAL_BUCKET_SIZE
#define LEAN_SCOPED_SET_INITIAL_BUCKET_SIZE 8
#endif
namespace lean {
/**
\brief Scoped sets (aka backtrackable sets).
*/
template<typename Key, typename Hash = std::hash<Key>, typename KeyEqual = std::equal_to<Key>>
class scoped_set {
typedef std::unordered_set<Key, Hash, KeyEqual> set;
typedef typename set::size_type size_type;
enum class action_kind { Insert, Erase };
set m_set;
std::vector<pair<action_kind, Key>> m_actions;
std::vector<unsigned> m_scopes;
public:
explicit scoped_set(size_type bucket_count = LEAN_SCOPED_SET_INITIAL_BUCKET_SIZE,
const Hash& hash = Hash(),
const KeyEqual& equal = KeyEqual()):
m_set(bucket_count, hash, equal) {
// the return type of Hash()(k) should be convertible to size_t
static_assert(std::is_convertible<typename std::result_of<decltype(std::declval<Hash>())(Key const &)>::type,
std::size_t>::value,
"The return type of hash function is not convertible to std::size_t");
// the return type of KeyEqual()(k1, k2) should be bool
static_assert(std::is_same<typename std::result_of<decltype(std::declval<KeyEqual>())(Key const &, Key const &)>::type,
bool>::value,
"The return type of KeyEqual()(k1, k2) is not bool");
}
/** \brief Return the number of scopes. */
unsigned num_scopes() const {
return m_scopes.size();
}
/** \brief Return true iff there are no scopes. */
bool at_base_lvl() const {
return m_scopes.empty();
}
/** \brief Create a new scope (it allows us to restore the current state of the set). */
void push() {
m_scopes.push_back(m_actions.size());
}
/** \brief Remove \c num scopes, and restores the state of the set. */
void pop(unsigned num = 1) {
lean_assert(num <= num_scopes());
unsigned old_sz = m_scopes[num_scopes() - num];
lean_assert(old_sz <= m_actions.size());
unsigned i = m_actions.size();
while (i > old_sz) {
--i;
auto const & p = m_actions.back();
if (p.first == action_kind::Insert) {
m_set.erase(p.second);
} else {
m_set.insert(p.second);
}
m_actions.pop_back();
}
lean_assert(m_actions.size() == old_sz);
m_scopes.resize(num_scopes() - num);
}
/** \brief Return true iff the set is empty */
bool empty() const {
return m_set.empty();
}
/** \brief Return the number of elements stored in the set. */
unsigned size() const {
return m_set.size();
}
/** \brief Insert an element in the set */
void insert(Key const & k) {
if (!at_base_lvl()) {
if (m_set.find(k) == m_set.end())
m_actions.emplace_back(action_kind::Insert, k);
}
m_set.insert(k);
}
/** \brief Remove an element from the set */
void erase(Key const & k) {
if (!at_base_lvl()) {
if (m_set.find(k) != m_set.end())
m_actions.emplace_back(action_kind::Erase, k);
}
m_set.erase(k);
}
/** \brief Remove all elements and scopes */
void clear() {
m_set.clear();
m_actions.clear();
m_scopes.clear();
}
typedef typename set::const_iterator const_iterator;
const_iterator find(Key const & k) const {
return m_set.find(k);
}
const_iterator begin() const {
return m_set.begin();
}
const_iterator end() const {
return m_set.end();
}
class mk_scope {
scoped_set & m_set;
public:
mk_scope(scoped_set & s):m_set(s) { m_set.push(); }
~mk_scope() { m_set.pop(); }
};
};
}