116 lines
4.6 KiB
C++
116 lines
4.6 KiB
C++
/*
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Copyright (c) 2016 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 <algorithm>
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#include "kernel/instantiate.h"
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#include "library/util.h"
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#include "library/app_builder.h"
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#include "library/constants.h"
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#include "library/trace.h"
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#include "library/check.h"
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#include "library/pp_options.h"
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#include "library/vm/vm_list.h"
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#include "library/vm/vm_option.h"
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#include "library/vm/vm_nat.h"
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#include "library/vm/vm_expr.h"
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#include "library/tactic/tactic_state.h"
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#include "library/tactic/occurrences.h"
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#include "library/tactic/kabstract.h"
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#include "library/tactic/clear_tactic.h"
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#include "library/tactic/assert_tactic.h"
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#include "library/tactic/rewrite_tactic.h"
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namespace lean {
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rewrite_cfg::rewrite_cfg(vm_obj const & cfg):apply_cfg(cfield(cfg, 0)) {
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m_symm = to_bool(cfield(cfg, 1));
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m_occs = to_occurrences(cfield(cfg, 2));
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}
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static vm_obj rewrite_core(expr h, expr e, rewrite_cfg const & cfg, tactic_state s) {
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optional<metavar_decl> g = s.get_main_goal_decl();
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if (!g) return mk_no_goals_exception(s);
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tactic_state_context_cache cache(s);
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type_context_old ctx = cache.mk_type_context(cfg.m_mode);
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type_context_old::approximate_scope _(ctx, cfg.m_approx);
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expr h_type = ctx.infer(h);
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/* Generate meta-variables for arguments */
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buffer<expr> metas;
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buffer<bool> is_instance;
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while (true) {
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h_type = ctx.relaxed_try_to_pi(h_type);
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if (!is_pi(h_type))
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break;
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expr meta = ctx.mk_metavar_decl(ctx.lctx(), binding_domain(h_type));
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is_instance.push_back(is_inst_implicit(binding_info(h_type)));
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metas.push_back(meta);
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h = mk_app(h, meta);
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h_type = instantiate(binding_body(h_type), meta);
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}
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expr A, lhs, rhs;
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if (is_iff(h_type, lhs, rhs)) {
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h = mk_app(mk_constant(get_propext_name()), lhs, rhs, h);
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h_type = mk_eq(ctx, lhs, rhs);
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}
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h_type = annotated_head_beta_reduce(h_type);
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if (!is_eq(h_type, A, lhs, rhs))
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return tactic::mk_exception("rewrite tactic failed, lemma is not an equality nor a iff", s);
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if (is_metavar(lhs))
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return tactic::mk_exception("rewrite tactic failed, lemma lhs is a metavariable", s);
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if (cfg.m_symm) {
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h = mk_eq_symm(ctx, h);
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h_type = mk_eq(ctx, rhs, lhs);
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std::swap(lhs, rhs);
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}
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e = ctx.instantiate_mvars(e);
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expr pattern = lhs;
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lean_trace("rewrite", tout() << "before kabstract\n";);
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expr e_abst = kabstract(ctx, e, pattern, cfg.m_occs, cfg.m_unify);
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if (!has_loose_bvars(e_abst)) {
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auto new_s = update_option_if_undef(s, get_pp_beta_name(), false);
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auto thunk = [=]() {
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format msg = format("rewrite tactic failed, did not find instance of the pattern in the target expression");
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msg += pp_indented_expr(new_s, pattern);
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return msg;
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};
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return tactic::mk_exception(thunk, new_s);
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}
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/* Synthesize type class instances */
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vm_obj out_error_obj;
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if (cfg.m_instances && !synth_instances(ctx, metas, is_instance, s, &out_error_obj, "rewrite"))
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return out_error_obj;
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/* Collect unassigned mvars */
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buffer<expr> new_goals;
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collect_new_goals(ctx, cfg.m_new_goals, metas, new_goals);
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/* Motive and resulting type */
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expr new_e = ctx.instantiate_mvars(instantiate(e_abst, rhs));
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expr e_eq_e = mk_eq(ctx, e, e);
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expr e_eq_e_abst = mk_app(app_fn(e_eq_e), e_abst);
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expr motive = mk_lambda("_a", A, e_eq_e_abst);
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try {
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type_context_old::transparency_scope scope(ctx, ensure_semireducible_mode(ctx.mode()));
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check(ctx, motive);
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} catch (exception & ex) {
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throw nested_exception("rewrite tactic failed, motive is not type correct", std::current_exception());
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}
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expr prf = mk_eq_ndrec(ctx, motive, mk_eq_refl(ctx, e), h);
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tactic_state new_s = set_mctx_goals(s, ctx.mctx(), append(cons(head(s.goals()), to_list(new_goals)), tail(s.goals())));
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return tactic::mk_success(mk_vm_pair(to_obj(new_e), mk_vm_pair(to_obj(prf), to_obj(to_list(metas)))), new_s);
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}
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vm_obj tactic_rewrite_core(vm_obj const & h, vm_obj const & e, vm_obj const & cfg, vm_obj const & s) {
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LEAN_TACTIC_TRY;
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return rewrite_core(to_expr(h), to_expr(e), rewrite_cfg(cfg), tactic::to_state(s));
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LEAN_TACTIC_CATCH(tactic::to_state(s));
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}
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void initialize_rewrite_tactic() {
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register_trace_class("rewrite");
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DECLARE_VM_BUILTIN(name({"tactic", "rewrite_core"}), tactic_rewrite_core);
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}
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void finalize_rewrite_tactic() {
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}
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}
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