mirror of
https://github.com/Z3Prover/z3
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284 lines
8.3 KiB
C++
284 lines
8.3 KiB
C++
/*++
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Copyright (c) 2017 Microsoft Corporation
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Module Name:
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injectivity_tactic.cpp
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Author:
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Nicolas Braud-Santoni (t-nibrau) 2017-08-10
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--*/
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#include <algorithm>
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#include <utility>
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#include "tactic/tactical.h"
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#include "ast/rewriter/rewriter_def.h"
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#include "tactic/core/injectivity_tactic.h"
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#include "util/dec_ref_util.h"
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class injectivity_tactic : public tactic {
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struct InjHelper : public obj_map<func_decl, obj_hashtable<func_decl>*> {
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ast_manager & m_manager;
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void insert(func_decl* const f, func_decl* const g) {
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obj_hashtable<func_decl> *m;
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if (! obj_map::find(f, m)) {
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m_manager.inc_ref(f);
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m = alloc(obj_hashtable<func_decl>); // TODO: Check we don't leak memory
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obj_map::insert(f, m);
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}
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if (!m->contains(g)) {
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m_manager.inc_ref(g);
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m->insert(g);
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}
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}
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bool find(func_decl* const f, func_decl* const g) const {
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obj_hashtable<func_decl> *m;
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if(! obj_map::find(f, m))
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return false;
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return m->contains(g);
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}
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InjHelper(ast_manager& m) : obj_map<func_decl, obj_hashtable<func_decl>*>(), m_manager(m) {}
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~InjHelper() {
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for(auto m : *this) {
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for (func_decl* f : *m.get_value())
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m_manager.dec_ref(f);
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m_manager.dec_ref(m.m_key);
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dealloc(m.m_value);
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}
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}
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};
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struct finder {
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ast_manager & m_manager;
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InjHelper & inj_map;
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finder(ast_manager & m, InjHelper & map, params_ref const & p) :
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m_manager(m),
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inj_map(map) {
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updt_params(p);
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}
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ast_manager & m() const { return m_manager; }
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bool is_axiom(expr* n, func_decl* &f, func_decl* &g) {
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if (!is_forall(n))
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return false;
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quantifier* const q = to_quantifier(n);
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if (q->get_num_decls() != 1)
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return false;
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const expr * const body = q->get_expr();
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// n ~= forall x. body
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if (!m().is_eq(body))
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return false;
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const app * const body_a = to_app(body);
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if (body_a->get_num_args() != 2)
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return false;
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const expr* a = body_a->get_arg(0);
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const expr* b = body_a->get_arg(1);
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// n ~= forall x. (= a b)
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if (is_app(a) && is_var(b)) {
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// Do nothing
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}
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else if (is_app(b) && is_var(a)) {
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std::swap(a, b);
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}
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else
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return false;
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const app* const a_app = to_app(a);
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const var* const b_var = to_var(b);
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if (b_var->get_idx() != 0) // idx is the De Bruijn's index
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return false;
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if (a_app->get_num_args() != 1)
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return false;
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g = a_app->get_decl();
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const expr* const a_body = a_app->get_arg(0);
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// n ~= forall x. (= (g a_body) x)
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if (!is_app(a_body))
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return false;
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const app* const a_body_app = to_app(a_body);
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if (a_body_app->get_num_args() != 1) // Maybe TODO: support multi-argument functions
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return false;
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f = a_body_app->get_decl();
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const expr* const a_body_body = a_body_app->get_arg(0);
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// n ~= forall x. (= (g (f a_body_body)) x)
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if (a_body_body != b_var)
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return false;
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// n ~= forall x. (= (g (f x)) x)
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return true;
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}
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void operator()(goal_ref const & goal,
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goal_ref_buffer & result) {
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tactic_report report("injectivity", *goal);
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fail_if_unsat_core_generation("injectivity", goal); // TODO: Support UNSAT cores
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fail_if_proof_generation("injectivity", goal);
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for (unsigned i = 0; i < goal->size(); ++i) {
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func_decl *f, *g;
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if (!is_axiom(goal->form(i), f, g)) continue;
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TRACE("injectivity", tout << "Marking " << f->get_name() << " as injective" << std::endl;);
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inj_map.insert(f, g);
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// TODO: Record that g is f's pseudoinverse
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}
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}
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void updt_params(params_ref const & p) {}
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};
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struct rewriter_eq_cfg : public default_rewriter_cfg {
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ast_manager & m_manager;
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InjHelper & inj_map;
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ast_manager & m() const { return m_manager; }
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rewriter_eq_cfg(ast_manager & m, InjHelper & map, params_ref const & p) : m_manager(m), inj_map(map) {
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}
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~rewriter_eq_cfg() {
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}
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void cleanup_buffers() {
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}
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void reset() {
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}
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br_status reduce_app(func_decl * f, unsigned num, expr * const * args, expr_ref & result, proof_ref & result_pr) {
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if (num != 2)
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return BR_FAILED;
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if (!m().is_eq(f))
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return BR_FAILED;
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// We are rewriting (= a b)
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if (!is_app(args[0]) || !is_app(args[1]))
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return BR_FAILED;
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const app* const a = to_app(args[0]);
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const app* const b = to_app(args[1]);
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// a and b are applications of the same function
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if (a->get_decl() != b->get_decl())
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return BR_FAILED;
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// Maybe TODO: Generalize to multi-parameter functions ?
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if (a->get_num_args() != 1 || b->get_num_args() != 1)
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return BR_FAILED;
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if (!inj_map.contains(a->get_decl()))
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return BR_FAILED;
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SASSERT(a->get_arg(0)->get_sort() == b->get_arg(0)->get_sort());
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TRACE("injectivity", tout << "Rewriting (= " << mk_ismt2_pp(args[0], m()) <<
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" " << mk_ismt2_pp(args[1], m()) << ")" << std::endl;);
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result = m().mk_eq(a->get_arg(0), b->get_arg(0));
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result_pr = nullptr;
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return BR_DONE;
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}
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};
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struct rewriter_eq : public rewriter_tpl<rewriter_eq_cfg> {
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rewriter_eq_cfg m_cfg;
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rewriter_eq(ast_manager & m, InjHelper & map, params_ref const & p) :
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rewriter_tpl<rewriter_eq_cfg>(m, m.proofs_enabled(), m_cfg),
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m_cfg(m, map, p) {
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}
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};
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struct rewriter_inverse { };
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finder * m_finder;
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rewriter_eq * m_eq;
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InjHelper * m_map;
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params_ref m_params;
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ast_manager & m_manager;
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public:
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injectivity_tactic(ast_manager & m, params_ref const & p):
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m_params(p),
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m_manager(m) {
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TRACE("injectivity", tout << "constructed new tactic" << std::endl;);
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m_map = alloc(InjHelper, m);
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m_finder = alloc(finder, m, *m_map, p);
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m_eq = alloc(rewriter_eq, m, *m_map, p);
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}
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tactic * translate(ast_manager & m) override {
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return alloc(injectivity_tactic, m, m_params);
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}
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~injectivity_tactic() override {
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dealloc(m_finder);
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dealloc(m_eq);
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dealloc(m_map);
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}
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char const* name() const override { return "injectivity"; }
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void updt_params(params_ref const & p) override {
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m_params.append(p);
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m_finder->updt_params(m_params);
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}
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void collect_param_descrs(param_descrs & r) override {
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insert_max_memory(r);
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insert_produce_models(r);
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}
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void operator()(goal_ref const & g,
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goal_ref_buffer & result) override {
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(*m_finder)(g, result);
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for (unsigned i = 0; i < g->size(); ++i) {
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expr* curr = g->form(i);
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expr_ref rw(m_manager);
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proof_ref pr(m_manager);
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(*m_eq)(curr, rw, pr);
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g->update(i, rw, pr, g->dep(i));
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}
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result.push_back(g.get());
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}
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void cleanup() override {
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InjHelper * m = alloc(InjHelper, m_manager);
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finder * f = alloc(finder, m_manager, *m, m_params);
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rewriter_eq * r = alloc(rewriter_eq, m_manager, *m, m_params);
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std::swap(m, m_map), std::swap(f, m_finder), std::swap(r, m_eq);
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dealloc(m), dealloc(f), dealloc(r);
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}
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};
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tactic * mk_injectivity_tactic(ast_manager & m, params_ref const & p) {
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return alloc(injectivity_tactic, m, p);
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}
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