63 lines
2.1 KiB
C
63 lines
2.1 KiB
C
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/*
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Copyright (c) 2015 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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*/
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#pragma once
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#include "library/blast/state.h"
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namespace lean {
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namespace blast {
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/** \brief Choice points are used different ways to proceed
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For example, given
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|- A \/ B
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we may proceed by trying to prove A or B. Each alternative
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is a different proof state. Actions my create choice points
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and add them to the choice point stack.
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*/
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class choice_point_cell {
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MK_LEAN_RC(); // Declare m_rc counter
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void dealloc() { delete this; }
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public:
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virtual ~choice_point_cell();
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/** \brief Return the next proof state. This method may
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perform destructive updates, choice points are not shared
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objects. */
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virtual optional<state> next() = 0;
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};
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/** \brief Smart pointer for choice points */
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class choice_point {
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choice_point_cell * m_ptr;
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public:
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choice_point():m_ptr(nullptr) {}
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choice_point(choice_point_cell * c):m_ptr(c) { m_ptr->inc_ref(); }
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choice_point(choice_point const & s):m_ptr(s.m_ptr) { if (m_ptr) m_ptr->inc_ref(); }
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choice_point(choice_point && s):m_ptr(s.m_ptr) { s.m_ptr = nullptr; }
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~choice_point() { if (m_ptr) m_ptr->dec_ref(); }
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choice_point & operator=(choice_point const & s) { LEAN_COPY_REF(s); }
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choice_point & operator=(choice_point && s) { LEAN_MOVE_REF(s); }
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optional<state> next() {
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lean_assert(m_ptr);
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return m_ptr->next();
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}
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};
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/** \brief Initialize thread local data-structures for storing choice points */
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void init_choice_points();
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/** \brief Add choice point to the top of the stack */
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void push_choice_point(choice_point const & c);
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/** \brief If there is another choice point, then update the current state and return true.
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Otherwise, return false. */
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bool next_choice_point();
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/** \brief Return size of the choice point stack */
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unsigned get_num_choice_points();
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/** \brief Shrink the size of the choice point stack.
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\pre n <= get_num_choice_points */
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void shrink_choice_points(unsigned n);
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/** \brief Clear/remove all choice points */
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void clear_choice_points();
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}}
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