lean2/src/kernel/universe_constraints.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_map>
#include <utility>
#include <functional>
#include <vector>
#include "util/name.h"
#include "util/hash.h"
#include "util/name_map.h"
#include "util/optional.h"
namespace lean {
/**
\brief Store the set of universe constraints.
It is based on Floyd-Warshall all-pairs shortest path algorithm.
*/
class universe_constraints {
typedef std::pair<name, int> edge;
typedef std::vector<edge> edges;
typedef name_map<edges> node_to_edges;
typedef std::pair<name, name> name_pair;
struct name_pair_hash_fn {
unsigned operator()(name_pair const & p) const { return hash(p.first.hash(), p.second.hash()); }
};
typedef std::unordered_map<name_pair, int, name_pair_hash_fn, std::equal_to<name_pair>> distances;
node_to_edges m_incoming_edges;
node_to_edges m_outgoing_edges;
distances m_distances;
public:
/**
\brief Add a new variable.
\pre The variables does not exist in this set of constraints.
*/
void add_var(name const & n);
/**
\brief Return true iff this set of constraints contains the variable n.
That is, it was added using add_var.
*/
bool contains(name const & n) const;
/** \brief Return true iff n1 >= n2 + k is implied by this set of constraints. */
bool is_implied(name const & n1, name const & n2, int k) const;
/** \brief Return true iff n1 < n2 + k is not implied by this set of constraints. */
bool is_consistent(name const & n1, name const & n2, int k) const;
/**
\brief Return true iff the constraint n1 >= n2 + k produces an integer overflow when added
to the set of constraints.
*/
bool overflows(name const & n1, name const & n2, int k) const;
/**
\brief Add new constraint n1 >= n2 + k.
\pre is_consistent(n1, n2, k)
\pre contains(n1)
\pre contains(n2)
*/
void add_constraint(name const & n1, name const & n2, int k);
/**
\brief Return the "distance" between n1 and n2.
That is, the best k s.t. n1 >= n2 + k is implied by this set of constraints
but n1 >= n2 + k + i is not for any i > 0.
If there is no such k, then return none.
*/
optional<int> get_distance(name const & n1, name const & n2) const;
};
}