142 lines
5.7 KiB
C++
142 lines
5.7 KiB
C++
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/*
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Copyright (c) 2014 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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*/
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#include "kernel/abstract.h"
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#include "kernel/instantiate.h"
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#include "kernel/inductive/inductive.h"
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#include "library/locals.h"
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#include "library/tactic/tactic.h"
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#include "library/reducible.h"
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#include "library/tactic/expr_to_tactic.h"
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namespace lean {
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static bool is_inversion_applicable(environment const & env, expr const & t) {
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expr const & fn = get_app_fn(t);
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if (!is_constant(fn))
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return false;
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if (!inductive::is_inductive_decl(env, const_name(fn)))
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return false;
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if (!env.find(name{const_name(fn), "cases_on"}) ||
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!env.find(name("eq")) || !env.find(name("heq")))
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return false;
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return true;
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}
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static pair<expr, expr> mk_eq(type_checker & tc, expr const & lhs, expr const & rhs) {
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expr lhs_type = tc.infer(lhs).first;
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expr rhs_type = tc.infer(rhs).first;
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constraint_seq cs;
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if (tc.is_def_eq(lhs_type, rhs_type, justification(), cs) && !cs) {
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level l = sort_level(tc.ensure_type(lhs_type).first);
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return mk_pair(mk_app(mk_constant("eq", to_list(l)), lhs_type, lhs, rhs),
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mk_app(mk_constant({"eq", "refl"}, to_list(l)), rhs_type, rhs));
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} else {
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level l = sort_level(tc.ensure_type(lhs_type).first);
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return mk_pair(mk_app(mk_constant("heq", to_list(l)), lhs_type, lhs, rhs_type, rhs),
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mk_app(mk_constant({"heq", "refl"}, to_list(l)), rhs_type, rhs));
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}
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}
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tactic generalize_indices_tactic(name const & n) {
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auto fn = [=](environment const & env, io_state const &, proof_state const & s) -> optional<proof_state> {
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goals const & gs = s.get_goals();
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if (empty(gs))
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return none_proof_state();
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goal g = head(gs);
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goals tail_gs = tail(gs);
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auto p = g.find_hyp(n);
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if (!p)
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return none_proof_state();
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expr const & h = p->first;
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name_generator ngen = s.get_ngen();
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auto tc = mk_type_checker(env, ngen.mk_child(), s.relax_main_opaque());
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expr h_type = tc->whnf(mlocal_type(h)).first;
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if (!is_inversion_applicable(env, h_type))
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return none_proof_state();
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buffer<expr> hyps;
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g.get_hyps(hyps);
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expr m = g.get_meta();
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expr m_type = g.get_type();
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auto new_subst = s.get_subst();
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name h_new_name = g.get_unused_name(local_pp_name(h));
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buffer<expr> I_args;
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expr const & I = get_app_args(h_type, I_args);
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// Set 1. generalize indices
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unsigned nindices = *inductive::get_num_indices(env, const_name(I));
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if (nindices > 0) {
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expr h_new_type = mk_app(I, I_args.size() - nindices, I_args.data());
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expr d = tc->whnf(tc->infer(h_new_type).first).first;
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unsigned eq_idx = 1;
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name eq_prefix("H");
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buffer<expr> ts;
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buffer<expr> eqs;
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buffer<expr> refls;
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for (unsigned i = I_args.size() - nindices; i < I_args.size(); i++) {
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expr t_type = binding_domain(d);
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expr t = mk_local(ngen.next(), g.get_unused_name(binding_name(d)), t_type, binder_info());
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expr const & index = I_args[i];
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pair<expr, expr> p = mk_eq(*tc, t, index);
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expr new_eq = p.first;
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expr new_refl = p.second;
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eqs.push_back(mk_local(ngen.next(), g.get_unused_name(eq_prefix, eq_idx), new_eq, binder_info()));
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refls.push_back(new_refl);
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h_new_type = mk_app(h_new_type, t);
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hyps.push_back(t);
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ts.push_back(t);
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d = instantiate(binding_body(d), t);
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}
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expr h_new = mk_local(ngen.next(), h_new_name, h_new_type, local_info(h));
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hyps.push_back(h_new);
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expr new_type = Pi(eqs, g.get_type());
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expr new_meta = mk_app(mk_metavar(ngen.next(), Pi(hyps, new_type)), hyps);
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goal new_g(new_meta, new_type);
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expr val = g.abstract(mk_app(mk_app(mk_app(Fun(ts, Fun(h_new, new_meta)), nindices, I_args.end() - nindices), h), refls));
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new_subst.assign(g.get_name(), val);
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proof_state new_s(s, goals(new_g, tail_gs), new_subst, ngen);
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return some_proof_state(new_s);
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} else {
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expr h_new = mk_local(ngen.next(), h_new_name, h_type, local_info(h));
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hyps.push_back(h_new);
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expr new_meta = mk_app(mk_metavar(ngen.next(), Pi(hyps, g.get_type())), hyps);
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goal new_g(new_meta, g.get_type());
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expr val = g.abstract(mk_app(new_meta, h));
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new_subst.assign(g.get_name(), val);
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proof_state new_s(s, goals(new_g, tail_gs), new_subst, ngen);
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return some_proof_state(new_s);
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}
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};
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return tactic01(fn);
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}
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tactic cases_on_tactic() {
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// TODO(Leo)
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return id_tactic();
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}
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tactic inversion_eqs_tactic() {
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// TODO(Leo)
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return id_tactic();
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}
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tactic inversion_clear_tactic() {
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// TODO(Leo)
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return id_tactic();
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}
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tactic inversion_tactic(name const & n) {
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return generalize_indices_tactic(n) << cases_on_tactic() << inversion_eqs_tactic() << inversion_clear_tactic();
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}
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void initialize_inversion_tactic() {
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register_tac(name({"tactic", "inversion"}),
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[](type_checker &, elaborate_fn const &, expr const & e, pos_info_provider const *) {
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name n = tactic_expr_to_id(app_arg(e), "invalid 'inversion' tactic, argument must be an identifier");
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return inversion_tactic(n);
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});
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}
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void finalize_inversion_tactic() {}
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}
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