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Preprocess away leading characters; otw. we are unsound

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This commit is contained in:
CEisenhofer 2026-06-09 14:44:41 +02:00
parent ad17fe71b1
commit 9b357373b0
2 changed files with 124 additions and 107 deletions
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43
src/smt/theory_nseq.cpp
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@ -457,6 +457,40 @@ namespace smt {
expr* const s = mem.m_str->get_expr();
std::cout << "Propagating: " << seq::mem_pp(mem, m) << std::endl;
if (!mem.m_str->is_empty()) {
if (mem.m_str->first()->is_char()) {
euf::snode* re_node = mem.m_regex;
euf::snode* str_node = mem.m_str;
do {
// eliminate leading character by derivatives
re_node = m_sgraph.brzozowski_deriv(re_node, mem.m_str->first());
str_node = m_sgraph.drop_first(str_node);
} while (!str_node->is_empty() && str_node->first()->is_char());
if (re_node->is_fail()) {
literal_vector lits;
lits.push_back(mem.lit);
set_conflict(lits);
return;
}
const expr_ref e(m_seq.re.mk_in_re(str_node->get_expr(), re_node->get_expr()), m);
ctx.mk_th_axiom(get_id(), ~mem.lit, mk_literal(e));
m_ignored_mem.insert(mem.lit);
ctx.push_trail(insert_map(m_ignored_mem, mem.lit));
return;
}
}
else {
// check nullability
if (m_sgraph.re_nullable(mem.m_regex) == l_true) {
// empty string in nullable regex → trivially satisfied
m_ignored_mem.insert(mem.lit);
ctx.push_trail(insert_map(m_ignored_mem, mem.lit));
return;
}
return;
}
if (mem.m_regex->is_full_seq()) {
// u \in .* can be ignored
m_ignored_mem.insert(mem.lit);
@ -510,6 +544,11 @@ namespace smt {
if (!get_fparams().m_nseq_regex_factorization_threshold)
return;
SASSERT(!mem.m_str->is_empty());
SASSERT(!mem.m_str->first()->is_char());
if (!mem.m_str->first()->is_var())
return;
// Eager sigma factorization (token-level): when enabled, split a non-primitive
// membership s ∈ r at the boundary between the first concat argument (head) and
// the rest (tail), using compute_sigma. This mirrors the lazy Nielsen
@ -553,12 +592,16 @@ namespace smt {
// forward direction; mk_literal Tseitin-encodes each conjunction
literal_vector lits;
lits.push_back(~mem.lit);
std::cout << "Decomposing into:\n";
for (auto const& sp : pairs) {
expr_ref mem_head(m_seq.re.mk_in_re(head, sp.m_p), m);
expr_ref mem_tail(m_seq.re.mk_in_re(tail, sp.m_q), m);
expr_ref conj(m.mk_and(mem_head, mem_tail), m);
lits.push_back(mk_literal(conj));
seq::dep_tracker dep = nullptr;
std::cout << seq::mem_pp(seq::str_mem(m_sgraph.mk(head), m_sgraph.mk(sp.m_p), dep), m) << " && " << seq::mem_pp(seq::str_mem(m_sgraph.mk(tail), m_sgraph.mk(sp.m_q), dep), m) << "\n";
}
std::cout << std::endl;
ctx.mk_th_axiom(get_id(), lits.size(), lits.data());
m_ignored_mem.insert(mem.lit);
ctx.push_trail(insert_map(m_ignored_mem, mem.lit));