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/********************* */
/*! \file strings.cpp
** \verbatim
** Top contributors (to current version):
** Tianyi Liang, Tim King
** This file is part of the CVC4 project.
** Copyright (c) 2009-2020 by the authors listed in the file AUTHORS
** in the top-level source directory) and their institutional affiliations.
** All rights reserved. See the file COPYING in the top-level source
** directory for licensing information.\endverbatim
**
** \brief Reasoning about strings with CVC4 via C++ API.
**
** A simple demonstration of reasoning about strings with CVC4 via C++ API.
**/
#include <iostream>
#include <cvc4/cvc4.h>
#include <cvc4/options/set_language.h>
using namespace CVC4;
int main() {
ExprManager em;
SmtEngine smt(&em);
// Set the logic
smt.setLogic("S");
// Produce models
smt.setOption("produce-models", true);
// The option strings-exp is needed
smt.setOption("strings-exp", true);
// Set output language to SMTLIB2
std::cout << language::SetLanguage(language::output::LANG_SMTLIB_V2);
// String type
Type string = em.stringType();
// std::string
std::string std_str_ab("ab");
// CVC4::String
CVC4::String cvc4_str_ab(std_str_ab);
CVC4::String cvc4_str_abc("abc");
// String constants
Expr ab = em.mkConst(cvc4_str_ab);
Expr abc = em.mkConst(CVC4::String("abc"));
// String variables
Expr x = em.mkVar("x", string);
Expr y = em.mkVar("y", string);
Expr z = em.mkVar("z", string);
// String concatenation: x.ab.y
Expr lhs = em.mkExpr(kind::STRING_CONCAT, x, ab, y);
// String concatenation: abc.z
Expr rhs = em.mkExpr(kind::STRING_CONCAT, abc, z);
// x.ab.y = abc.z
Expr formula1 = em.mkExpr(kind::EQUAL, lhs, rhs);
// Length of y: |y|
Expr leny = em.mkExpr(kind::STRING_LENGTH, y);
// |y| >= 0
Expr formula2 = em.mkExpr(kind::GEQ, leny, em.mkConst(Rational(0)));
// Regular expression: (ab[c-e]*f)|g|h
Expr r = em.mkExpr(kind::REGEXP_UNION,
em.mkExpr(kind::REGEXP_CONCAT,
em.mkExpr(kind::STRING_TO_REGEXP, em.mkConst(String("ab"))),
em.mkExpr(kind::REGEXP_STAR,
em.mkExpr(kind::REGEXP_RANGE, em.mkConst(String("c")), em.mkConst(String("e")))),
em.mkExpr(kind::STRING_TO_REGEXP, em.mkConst(String("f")))),
em.mkExpr(kind::STRING_TO_REGEXP, em.mkConst(String("g"))),
em.mkExpr(kind::STRING_TO_REGEXP, em.mkConst(String("h"))));
// String variables
Expr s1 = em.mkVar("s1", string);
Expr s2 = em.mkVar("s2", string);
// String concatenation: s1.s2
Expr s = em.mkExpr(kind::STRING_CONCAT, s1, s2);
// s1.s2 in (ab[c-e]*f)|g|h
Expr formula3 = em.mkExpr(kind::STRING_IN_REGEXP, s, r);
// Make a query
Expr q = em.mkExpr(kind::AND,
formula1,
formula2,
formula3);
// check sat
Result result = smt.checkSat(q);
std::cout << "CVC4 reports: " << q << " is " << result << "." << std::endl;
if(result == Result::SAT) {
std::cout << " x = " << smt.getValue(x) << std::endl;
std::cout << " s1.s2 = " << smt.getValue(s) << std::endl;
}
}
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