Theory of Bags

examples/api/cpp/bags.cpp

  1/******************************************************************************
  2 * This file is part of the cvc5 project.
  3 *
  4 * Copyright (c) 2009-2026 by the authors listed in the file AUTHORS
  5 * in the top-level source directory and their institutional affiliations.
  6 * All rights reserved.  See the file COPYING in the top-level source
  7 * directory for licensing information.
  8 * ****************************************************************************
  9 *
 10 * A simple demonstration of reasoning about bags.
 11 */
 12
 13#include <cvc5/cvc5.h>
 14
 15#include <iostream>
 16
 17using namespace std;
 18using namespace cvc5;
 19
 20int main()
 21{
 22  TermManager tm;
 23  Solver slv(tm);
 24  slv.setLogic("ALL");
 25  // Produce models
 26  slv.setOption("produce-models", "true");
 27  slv.setOption("incremental", "true");
 28
 29  Sort bag = tm.mkBagSort(tm.getStringSort());
 30  Term A = tm.mkConst(bag, "A");
 31  Term B = tm.mkConst(bag, "B");
 32  Term C = tm.mkConst(bag, "C");
 33  Term x = tm.mkConst(tm.getStringSort(), "x");
 34
 35  Term intersectionAC = tm.mkTerm(Kind::BAG_INTER_MIN, {A, C});
 36  Term intersectionBC = tm.mkTerm(Kind::BAG_INTER_MIN, {B, C});
 37
 38  // union disjoint does not distribute over intersection
 39  {
 40    Term unionDisjointAB = tm.mkTerm(Kind::BAG_UNION_DISJOINT, {A, B});
 41    Term lhs = tm.mkTerm(Kind::BAG_INTER_MIN, {unionDisjointAB, C});
 42    Term rhs =
 43        tm.mkTerm(Kind::BAG_UNION_DISJOINT, {intersectionAC, intersectionBC});
 44    Term guess = tm.mkTerm(Kind::EQUAL, {lhs, rhs});
 45    cout << "cvc5 reports: " << guess.notTerm() << " is "
 46         << slv.checkSatAssuming(guess.notTerm()) << "." << endl;
 47
 48    cout << A << ": " << slv.getValue(A) << endl;
 49    cout << B << ": " << slv.getValue(B) << endl;
 50    cout << C << ": " << slv.getValue(C) << endl;
 51    cout << lhs << ": " << slv.getValue(lhs) << endl;
 52    cout << rhs << ": " << slv.getValue(rhs) << endl;
 53  }
 54
 55  // union max distributes over intersection
 56  {
 57    Term unionMaxAB = tm.mkTerm(Kind::BAG_UNION_MAX, {A, B});
 58    Term lhs = tm.mkTerm(Kind::BAG_INTER_MIN, {unionMaxAB, C});
 59    Term rhs = tm.mkTerm(Kind::BAG_UNION_MAX, {intersectionAC, intersectionBC});
 60    Term theorem = tm.mkTerm(Kind::EQUAL, {lhs, rhs});
 61    cout << "cvc5 reports: " << theorem.notTerm() << " is "
 62         << slv.checkSatAssuming(theorem.notTerm()) << "." << endl;
 63  }
 64
 65  // Verify emptbag is a subbag of any bag
 66  {
 67    Term emptybag = tm.mkEmptyBag(bag);
 68    Term theorem = tm.mkTerm(Kind::BAG_SUBBAG, {emptybag, A});
 69
 70    cout << "cvc5 reports: " << theorem.notTerm() << " is "
 71         << slv.checkSatAssuming(theorem.notTerm()) << "." << endl;
 72  }
 73
 74  // find an element with multiplicity 4 in the disjoint union of
 75  // ; {|"a", "a", "b", "b", "b"|} and {|"b", "c", "c"|}
 76
 77  {
 78    Term one = tm.mkInteger(1);
 79    Term two = tm.mkInteger(2);
 80    Term three = tm.mkInteger(3);
 81    Term four = tm.mkInteger(4);
 82    Term a = tm.mkString("a");
 83    Term b = tm.mkString("b");
 84    Term c = tm.mkString("c");
 85
 86    Term bag_a_2 = tm.mkTerm(Kind::BAG_MAKE, {a, two});
 87    Term bag_b_3 = tm.mkTerm(Kind::BAG_MAKE, {b, three});
 88    Term bag_b_1 = tm.mkTerm(Kind::BAG_MAKE, {b, one});
 89    Term bag_c_2 = tm.mkTerm(Kind::BAG_MAKE, {c, two});
 90    Term bag_a_2_b_3 = tm.mkTerm(Kind::BAG_UNION_DISJOINT, {bag_a_2, bag_b_3});
 91    Term bag_b_1_c_2 = tm.mkTerm(Kind::BAG_UNION_DISJOINT, {bag_b_1, bag_c_2});
 92    Term union_disjoint =
 93        tm.mkTerm(Kind::BAG_UNION_DISJOINT, {bag_a_2_b_3, bag_b_1_c_2});
 94
 95    Term count_x = tm.mkTerm(Kind::BAG_COUNT, {x, union_disjoint});
 96    Term e = tm.mkTerm(Kind::EQUAL, {four, count_x});
 97    Result result = slv.checkSatAssuming(e);
 98
 99    cout << "cvc5 reports: " << e << " is " << result << "." << endl;
100    if (result.isSat())
101    {
102      cout << x << ": " << slv.getValue(x) << endl;
103    }
104  }
105}