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https://github.com/Z3Prover/z3
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0bdec633d7
Add theory_nseq, a Nielsen-graph-based string solver plugin for Z3. ## New files - src/smt/nseq_state.h/.cpp: constraint store bridging SMT context to Nielsen graph with manual push/pop backtracking - src/smt/nseq_regex.h/.cpp: regex membership handling via Brzozowski derivatives (stub delegates to sgraph::brzozowski_deriv) - src/smt/nseq_model.h/.cpp: model generation stub - src/smt/theory_nseq.h/.cpp: main theory class implementing smt::theory with its own private egraph/sgraph, returns FC_GIVEUP as skeleton - src/test/nseq_basic.cpp: unit tests covering instantiation, parameter validation, trivial-equality SAT, and node simplification ## Extensions to seq_nielsen.h/.cpp - Add search_result enum and solve() iterative-deepening DFS entry point - Add search_dfs() recursive DFS driver - Add simplify_node(), generate_extensions(), collect_conflict_deps() - Add nielsen_node::simplify_and_init(): trivial removal, empty propagation, prefix matching, symbol clash detection - Add nielsen_node::is_satisfied(), is_subsumed_by() - Implement Det, Const Nielsen, and Eq-split modifiers in generate_extensions() ## Integration - smt_params.cpp: accept 'nseq' as valid string_solver value - smt_params_helper.pyg: document 'nseq' option - smt_setup.h/.cpp: add setup_nseq(), wire into setup_QF_S() and setup_seq_str() - smt/CMakeLists.txt: add new sources and smt_seq dependency Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
66 lines
2 KiB
C++
66 lines
2 KiB
C++
/*++
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Copyright (c) 2026 Microsoft Corporation
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Module Name:
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nseq_regex.h
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Abstract:
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Regex membership handling using Brzozowski derivatives.
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Processes str_mem constraints after character consumption.
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Author:
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Nikolaj Bjorner (nbjorner) 2026-03-01
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--*/
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#pragma once
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#include "ast/euf/euf_sgraph.h"
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#include "smt/seq/seq_nielsen.h"
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namespace smt {
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class nseq_regex {
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euf::sgraph& m_sg;
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public:
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nseq_regex(euf::sgraph& sg) : m_sg(sg) {}
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// check if a regex snode represents the empty language
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bool is_empty_regex(euf::snode* re) const {
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return re && re->is_fail();
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}
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// compute derivative of regex re with respect to char elem and
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// return a new str_mem for the resulting constraint
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seq::str_mem derive(seq::str_mem const& mem, euf::snode* elem) {
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euf::snode* deriv = m_sg.brzozowski_deriv(mem.m_regex, elem);
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euf::snode* new_str = m_sg.drop_first(mem.m_str);
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return seq::str_mem(new_str, deriv, mem.m_history, mem.m_id, mem.m_dep);
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}
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// process a regex membership constraint after one character has been consumed
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// returns false if the resulting regex is empty (conflict)
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bool process_str_mem(seq::str_mem const& mem,
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vector<seq::str_mem>& out_mems) {
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if (!mem.m_str || !mem.m_regex)
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return true;
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// if regex does not accept the empty string and the string side is empty, conflict
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if (mem.m_str->is_empty()) {
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return mem.m_regex->is_nullable();
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}
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// compute minterms for the regex
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euf::snode_vector minterms;
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m_sg.compute_minterms(mem.m_regex, minterms);
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for (euf::snode* ch : minterms) {
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seq::str_mem new_mem = derive(mem, ch);
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if (!is_empty_regex(new_mem.m_regex))
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out_mems.push_back(new_mem);
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}
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return true;
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}
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};
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}
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