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https://github.com/Z3Prover/z3
synced 2025-04-29 20:05:51 +00:00
add evaluation of array equalities to model evaluator
Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner
parent
f6aaa5cc8d
commit
03336ab9f2
3 changed files with 273 additions and 4 deletions
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@ -258,7 +258,7 @@ final_check_status theory_seq::final_check_eh() {
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TRACE("seq", tout << ">>fixed_length\n";);
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return FC_CONTINUE;
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}
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if (branch_variable()) {
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if (reduce_length_eq() || branch_variable_mb() || branch_variable()) {
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++m_stats.m_branch_variable;
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TRACE("seq", tout << ">>branch_variable\n";);
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return FC_CONTINUE;
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@ -291,8 +291,7 @@ final_check_status theory_seq::final_check_eh() {
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return FC_GIVEUP;
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}
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bool theory_seq::branch_variable() {
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bool theory_seq::reduce_length_eq() {
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context& ctx = get_context();
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unsigned sz = m_eqs.size();
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int start = ctx.get_random_value();
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@ -304,7 +303,182 @@ bool theory_seq::branch_variable() {
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return true;
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}
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}
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return false;
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}
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bool theory_seq::branch_variable_mb() {
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context& ctx = get_context();
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unsigned sz = m_eqs.size();
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int start = ctx.get_random_value();
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bool change = false;
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for (unsigned i = 0; i < sz; ++i) {
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unsigned k = (i + start) % sz;
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eq const& e = m_eqs[i];
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vector<rational> len1, len2;
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if (!enforce_length(e.ls(), len1) || !enforce_length(e.rs(), len2)) {
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change = true;
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continue;
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}
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if (e.ls().empty() || e.rs().empty() || (!is_var(e.ls()[0]) && !is_var(e.rs()[0]))) {
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continue;
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}
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rational l1, l2;
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for (unsigned i = 0; i < len1.size(); ++i) l1 += len1[i];
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for (unsigned i = 0; i < len2.size(); ++i) l2 += len2[i];
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if (l1 != l2) {
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TRACE("seq", tout << "lengths are not compatible\n";);
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expr_ref l = mk_concat(e.ls().size(), e.ls().c_ptr());
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expr_ref r = mk_concat(e.rs().size(), e.rs().c_ptr());
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expr_ref lnl(m_util.str.mk_length(l), m), lnr(m_util.str.mk_length(r), m);
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add_axiom(~mk_eq(l, r, false), mk_eq(lnl, lnr, false));
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change = true;
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continue;
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}
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if (split_lengths(e.dep(), e.ls(), e.rs(), len1, len2)) {
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return true;
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}
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}
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return change;
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}
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/*
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\brief Decompose ls = rs into Xa = bYc, such that
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1.
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- X != Y
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- |b| <= |X| <= |bY| in currrent model
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- b is non-empty.
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2. X != Y
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- b is empty
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- |X| <= |Y|
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3. |X| = 0
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- propagate X = empty
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*/
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bool theory_seq::split_lengths(dependency* dep,
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expr_ref_vector const& ls, expr_ref_vector const& rs,
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vector<rational> const& ll, vector<rational> const& rl) {
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context& ctx = get_context();
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expr_ref X(m), Y(m), b(m);
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if (ls.empty() || rs.empty()) {
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return false;
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}
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if (is_var(ls[0]) && ll[0].is_zero()) {
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return set_empty(ls[0]);
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}
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if (is_var(rs[0]) && rl[0].is_zero()) {
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return set_empty(rs[0]);
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}
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if (is_var(rs[0]) && !is_var(ls[0])) {
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return split_lengths(dep, rs, ls, rl, ll);
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}
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if (!is_var(ls[0])) {
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return false;
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}
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X = ls[0];
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rational lenX = ll[0];
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expr_ref_vector bs(m);
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SASSERT(lenX.is_pos());
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rational lenB(0), lenY(0);
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for (unsigned i = 0; lenX > lenB && i < rs.size(); ++i) {
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bs.push_back(rs[i]);
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lenY = rl[i];
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lenB += lenY;
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}
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SASSERT(lenX <= lenB);
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SASSERT(!bs.empty());
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Y = bs.back();
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bs.pop_back();
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if (!is_var(Y) && !m_util.str.is_unit(Y)) {
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TRACE("seq", tout << "TBD: non variable or unit split: " << Y << "\n";);
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return false;
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}
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if (X == Y) {
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TRACE("seq", tout << "Cycle: " << X << "\n";);
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return false;
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}
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if (lenY.is_zero()) {
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return set_empty(Y);
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}
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b = mk_concat(bs, m.get_sort(X));
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SASSERT(X != Y);
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expr_ref split_pred = mk_skolem(symbol("seq.split"), X, b, Y, m.mk_bool_sort());
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literal split_predl = mk_literal(split_pred);
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lbool is_split = ctx.get_assignment(split_predl);
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if (is_split != l_true) {
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// split_pred <=> |b| < |X| <= |b| + |Y|
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expr_ref lenX(m_util.str.mk_length(X), m);
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expr_ref lenY(m_util.str.mk_length(Y), m);
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expr_ref lenb(m_util.str.mk_length(b), m);
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expr_ref le1(m_autil.mk_le(mk_sub(lenX, lenb), m_autil.mk_int(0)), m);
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expr_ref le2(m_autil.mk_le(mk_sub(mk_sub(lenX, lenb), lenY),
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m_autil.mk_int(0)), m);
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literal lit1(~mk_literal(le1));
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literal lit2(mk_literal(le2));
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add_axiom(~split_predl, lit1);
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add_axiom(~split_predl, lit2);
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add_axiom(split_predl, ~lit1, ~lit2);
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}
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else if (m_util.str.is_unit(Y)) {
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SASSERT(lenB == lenX);
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SASSERT(is_split == l_true);
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bs.push_back(Y);
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expr_ref bY(m_util.str.mk_concat(bs), m);
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literal_vector lits;
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lits.push_back(split_predl);
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propagate_eq(dep, lits, X, bY, true);
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}
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else {
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SASSERT(is_var(Y));
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// split_pred => X = bY1, Y = Y1Y2
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SASSERT(is_split == l_true);
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expr_ref Y1(mk_skolem(symbol("seq.left"), Y), m);
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expr_ref Y2(mk_skolem(symbol("seq.right"), Y), m);
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expr_ref bY1(m_util.str.mk_concat(b, Y1), m);
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expr_ref Y1Y2(m_util.str.mk_concat(Y1, Y2), m);
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literal_vector lits;
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lits.push_back(split_predl);
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propagate_eq(dep, lits, X, bY1, true);
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propagate_eq(dep, lits, Y, Y1Y2, true);
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}
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return true;
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}
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bool theory_seq::set_empty(expr* x) {
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add_axiom(~mk_eq(m_autil.mk_int(0), m_util.str.mk_length(x), false), mk_eq_empty(x));
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return true;
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}
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bool theory_seq::enforce_length(expr_ref_vector const& es, vector<rational> & len) {
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bool all_have_length = true;
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rational val;
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zstring s;
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for (unsigned i = 0; i < es.size(); ++i) {
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expr* e = es[i];
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if (m_util.str.is_unit(e)) {
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len.push_back(rational(1));
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}
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else if (m_util.str.is_empty(e)) {
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len.push_back(rational(0));
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}
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else if (m_util.str.is_string(e, s)) {
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len.push_back(rational(s.length()));
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}
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else if (get_length(e, val)) {
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len.push_back(val);
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}
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else {
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enforce_length(ensure_enode(e));
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all_have_length = false;
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}
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}
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return all_have_length;
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}
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bool theory_seq::branch_variable() {
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context& ctx = get_context();
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unsigned sz = m_eqs.size();
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int start = ctx.get_random_value();
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unsigned s = 0;
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for (unsigned i = 0; i < sz; ++i) {
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@ -3050,6 +3224,9 @@ void theory_seq::assign_eh(bool_var v, bool is_true) {
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else if (m_util.str.is_in_re(e)) {
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propagate_in_re(e, is_true);
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}
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else if (is_skolem(symbol("seq.split"), e)) {
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// propagate equalities
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}
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else {
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UNREACHABLE();
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}
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