lean2/src/library/blast/simplifier.cpp

611 lines
20 KiB
C++

/*
Copyright (c) 2015 Daniel Selsam. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Author: Daniel Selsam
*/
#include "kernel/abstract.h"
#include "kernel/expr_maps.h"
#include "kernel/instantiate.h"
#include "library/constants.h"
#include "library/expr_lt.h"
#include "library/class_instance_resolution.h"
#include "library/relation_manager.h"
#include "library/blast/expr.h"
#include "library/blast/blast_exception.h"
#include "library/blast/blast.h"
#include "library/blast/simplifier.h"
#include "library/simplifier/simp_rule_set.h"
#include "library/simplifier/ceqv.h"
#include "library/app_builder.h"
#include "util/flet.h"
#include "util/pair.h"
#include "util/sexpr/option_declarations.h"
#include <array>
#include <iostream> // TODO just for occasional debugging
#ifndef LEAN_DEFAULT_SIMPLIFY_MAX_STEPS
#define LEAN_DEFAULT_SIMPLIFY_MAX_STEPS 100
#endif
#ifndef LEAN_DEFAULT_SIMPLIFY_TOP_DOWN
#define LEAN_DEFAULT_SIMPLIFY_TOP_DOWN false
#endif
#ifndef LEAN_DEFAULT_SIMPLIFY_EXHAUSTIVE
#define LEAN_DEFAULT_SIMPLIFY_EXHAUSTIVE true
#endif
#ifndef LEAN_DEFAULT_SIMPLIFY_MEMOIZE
#define LEAN_DEFAULT_SIMPLIFY_MEMOIZE true
#endif
#ifndef LEAN_DEFAULT_SIMPLIFY_CONTEXTUAL
#define LEAN_DEFAULT_SIMPLIFY_CONTEXTUAL true
#endif
#ifndef LEAN_DEFAULT_SIMPLIFY_EXPAND_MACROS
#define LEAN_DEFAULT_SIMPLIFY_EXPAND_MACROS false
#endif
#ifndef LEAN_DEFAULT_SIMPLIFY_TRACE
#define LEAN_DEFAULT_SIMPLIFY_TRACE false
#endif
namespace lean {
namespace blast {
using simp::result;
/* Options */
static name * g_simplify_max_steps = nullptr;
static name * g_simplify_top_down = nullptr;
static name * g_simplify_exhaustive = nullptr;
static name * g_simplify_memoize = nullptr;
static name * g_simplify_contextual = nullptr;
static name * g_simplify_expand_macros = nullptr;
static name * g_simplify_trace = nullptr;
unsigned get_simplify_max_steps() {
return ios().get_options().get_unsigned(*g_simplify_max_steps, LEAN_DEFAULT_SIMPLIFY_MAX_STEPS);
}
bool get_simplify_top_down() {
return ios().get_options().get_bool(*g_simplify_top_down, LEAN_DEFAULT_SIMPLIFY_TOP_DOWN);
}
bool get_simplify_exhaustive() {
return ios().get_options().get_bool(*g_simplify_exhaustive, LEAN_DEFAULT_SIMPLIFY_EXHAUSTIVE);
}
bool get_simplify_memoize() {
return ios().get_options().get_bool(*g_simplify_memoize, LEAN_DEFAULT_SIMPLIFY_MEMOIZE);
}
bool get_simplify_contextual() {
return ios().get_options().get_bool(*g_simplify_contextual, LEAN_DEFAULT_SIMPLIFY_CONTEXTUAL);
}
bool get_simplify_expand_macros() {
return ios().get_options().get_bool(*g_simplify_expand_macros, LEAN_DEFAULT_SIMPLIFY_EXPAND_MACROS);
}
bool get_simplify_trace() {
return ios().get_options().get_bool(*g_simplify_trace, LEAN_DEFAULT_SIMPLIFY_TRACE);
}
/* Main simplifier class */
class simplifier {
blast_tmp_type_context m_tmp_tctx;
app_builder m_app_builder;
branch m_branch;
name m_rel;
list<expr> m_local_ctx;
/* Logging */
unsigned m_num_steps{0};
unsigned m_depth{0};
/* Options */
unsigned m_max_steps{get_simplify_max_steps()};
bool m_top_down{get_simplify_top_down()};
bool m_exhaustive{get_simplify_exhaustive()};
bool m_memoize{get_simplify_memoize()};
bool m_contextual{get_simplify_contextual()};
bool m_expand_macros{get_simplify_expand_macros()};
bool m_trace{get_simplify_trace()};
/* Cache */
expr_bi_struct_map<result> m_simplify_cache{};
/* Masks for building applications */
std::array<bool,6> eq_rec_all_mask{{true,true,true,true,true,true}};
/* Basic helpers */
bool using_eq() { return m_rel == get_eq_name(); }
bool is_dependent_fn(expr const & f) {
expr f_type = m_tmp_tctx->whnf(m_tmp_tctx->infer(f));
lean_assert(is_pi(f_type));
return has_free_vars(binding_body(f_type));
}
/* Results */
result lift_from_eq(expr const & x, result const & r);
result join(result const & r1, result const & r2);
result funext(result const & r, expr const & l);
result finalize(result const & r);
/* Simplification */
result simplify(expr const & e);
result simplify_lambda(expr const & e);
result simplify_pi(expr const & e);
result simplify_app(expr const & e);
result simplify_fun(expr const & e);
/* Rewriting */
result rewrite(expr const & e);
result rewrite(expr const & e, simp_rule const & sr);
void init_tmp_tctx_for(simp_rule_core const & sr);
/* Congruence */
result congr(result const & r_f, result const & r_arg);
result congr_fun(result const & r_f, expr const & arg);
result congr_arg(expr const & f, result const & r_arg);
result congr_funs(result const & r_f, buffer<expr> const & args);
result try_congrs(expr const & e);
result try_congr(expr const & e, congr_rule const & cr);
public:
simplifier(branch const & b, name const & rel);
result operator()(expr const & e) { return simplify(e); }
};
/* Constructor */
simplifier::simplifier(branch const & b, name const & rel):
m_app_builder(*m_tmp_tctx), m_branch(b), m_rel(rel) { }
/* Results */
result simplifier::lift_from_eq(expr const & x, result const & r) {
lean_assert(!r.is_none());
expr l = m_tmp_tctx->mk_tmp_local(m_tmp_tctx->infer(x));
auto motive_local = m_app_builder.mk_app(m_rel,x,l);
lean_assert(motive_local);
expr motive = Fun(l,*motive_local);
auto Rxx = m_app_builder.mk_refl(m_rel,x);
lean_assert(Rxx);
auto pf = m_app_builder.mk_eq_rec(motive,*Rxx,r.get_proof());
return result(r.get_new(),pf);
}
result simplifier::join(result const & r1, result const & r2) {
/* Assumes that both results are with respect to the same relation */
if (r1.is_none()) {
return r2;
}
else if (r2.is_none()) {
return r1;
}
else {
auto trans = m_app_builder.mk_trans(m_rel,r1.get_proof(),r2.get_proof());
lean_assert(trans);
return result(r2.get_new(),*trans);
}
}
result simplifier::funext(result const & r, expr const & l) {
// theorem funext {f₁ f₂ : Πx : A, B x} : (∀x, f₁ x = f₂ x) → f₁ = f₂ :=
lean_assert(!r.is_none());
expr e = Fun(l,r.get_new());
if (auto pf = m_app_builder.mk_app(get_funext_name(),Fun(l,r.get_proof())))
return result(e,*pf);
else
throw blast_exception("failed on [funext] matching",e);
}
result simplifier::finalize(result const & r) {
if (!r.is_none()) return r;
if (auto pf = m_app_builder.mk_refl(m_rel,r.get_new()))
return result(r.get_new(),*pf);
else
throw blast_exception("failed on [refl] matching",r.get_new());
}
/* Simplification */
result simplifier::simplify(expr const & e) {
m_num_steps++;
flet<unsigned> inc_depth(m_depth, m_depth+1);
if (m_trace) {
ios().get_diagnostic_channel() << m_num_steps << "." << m_depth << "." << m_rel << ": " << e << "\n";
}
if (m_num_steps > m_max_steps)
throw blast_exception("simplifier failed, maximum number of steps exceeded", e);
if (m_memoize) {
auto it = m_simplify_cache.find(e);
if (it != m_simplify_cache.end()) return it->second;
}
result r(e);
if (m_top_down) r = join(r, rewrite(whnf(r.get_new())));
r.update(whnf(r.get_new()));
switch (r.get_new().kind()) {
case expr_kind::Local:
case expr_kind::Meta:
case expr_kind::Sort:
case expr_kind::Constant:
// no-op
break;
case expr_kind::Var:
lean_unreachable();
case expr_kind::Macro:
/* TODO
if (m_expand_macros) {
if (auto m = blast::expand_macro(e)) r = join(r,simplify(whnf(*m)));
}
*/
break;
case expr_kind::Lambda:
if (using_eq()) r = join(r,simplify_lambda(r.get_new()));
break;
case expr_kind::Pi:
r = join(r,simplify_pi(r.get_new()));
break;
case expr_kind::App:
r = join(r,simplify_app(r.get_new()));
break;
}
if (!m_top_down) r = join(r,rewrite(whnf(r.get_new())));
if (r.get_new() == e && !using_eq()) {
{
flet<name> use_eq(m_rel, get_eq_name());
r = simplify(r.get_new());
}
if (!r.is_none()) r = lift_from_eq(e,r);
}
if (m_exhaustive && r.get_new() != e) r = join(r,simplify(r.get_new()));
if (m_memoize) m_simplify_cache.insert(mk_pair(e, r));
return r;
}
result simplifier::simplify_lambda(expr const & _e) {
lean_assert(is_lambda(_e));
expr e = _e;
buffer<expr> ls;
while (is_lambda(e)) {
expr d = instantiate_rev(binding_domain(e), ls.size(), ls.data());
expr l = m_tmp_tctx->mk_tmp_local(d,binding_info(e));
ls.push_back(l);
e = instantiate(binding_body(e),l);
}
result r = simplify(e);
if (r.is_none()) { return result(_e); }
for (int i = ls.size() - 1; i >= 0; --i) r = funext(r,ls[i]);
return r;
}
result simplifier::simplify_pi(expr const & e) {
lean_assert(is_pi(e));
return try_congrs(e);
}
result simplifier::simplify_app(expr const & e) {
lean_assert(is_app(e));
// TODO simplify operator as well, in cases (1) and (2)
/* (1) Try user-defined congruences */
result r = try_congrs(e);
if (!r.is_none()) {
if (using_eq()) return join(r,simplify_fun(r.get_new()));
else return r;
}
/* (2) Synthesize congruence lemma */
if (using_eq()) {
// TODO
}
/* (3) Fall back on generic binary congruence */
if (using_eq()) {
expr const & f = app_fn(e);
expr const & arg = app_arg(e);
result r_f = simplify(f);
if (is_dependent_fn(f)) {
if (r_f.is_none()) return e;
else return congr_fun(r_f,arg);
}
else {
result r_arg = simplify(arg);
if (r_f.is_none() && r_arg.is_none()) return e;
else if (r_f.is_none()) return congr_arg(f,r_arg);
else if (r_arg.is_none()) return congr_fun(r_f,arg);
else return congr(r_f,r_arg);
}
}
return result(e);
}
result simplifier::simplify_fun(expr const & e) {
lean_assert(is_app(e));
buffer<expr> args;
expr const & f = get_app_args(e, args);
result r_f = simplify(f);
if (r_f.is_none()) return result(e);
else return congr_funs(simplify(f),args);
}
/* Rewriting */
result simplifier::rewrite(expr const & e) {
result r(e);
/* First, we rewrite with local hypotheses */
//TODO
/* Next, we rewrite with the [simp_rule_set] */
simp_rule_set const * sr = get_simp_rule_sets(env()).find(m_rel);
if (!sr) return r;
list<simp_rule> const * srs = sr->find_simp(e);
if (!srs) return r;
for_each(*srs,[&](simp_rule const & sr) { r = join(r,rewrite(r.get_new(),sr)); });
return r;
}
result simplifier::rewrite(expr const & e, simp_rule const & sr) {
blast_tmp_type_context tmp_tctx(sr.get_num_umeta(),sr.get_num_emeta());
if (!tmp_tctx->is_def_eq(e,sr.get_lhs())) return result(e);
/* Traverse metavariables backwards */
for (int i = sr.get_num_emeta() - 1; i >= 0; --i) {
expr const & m = sr.get_emeta(i);
bool is_instance = sr.is_instance(i);
if (is_instance) {
expr type = tmp_tctx->instantiate_uvars_mvars(tmp_tctx->infer(m));
if (auto v = tmp_tctx->mk_class_instance(type)) {
if (!tmp_tctx->force_assign(m, *v))
return result(e);
} else {
return result(e);
}
}
if (tmp_tctx->is_mvar_assigned(i)) continue;
if (tmp_tctx->is_prop(tmp_tctx->infer(m))) {
// TODO try to prove
return result(e);
}
/* We fail if there is a meta variable that we still cannot assign */
return result(e);
}
for (unsigned i = 0; i < sr.get_num_umeta(); i++) {
if (!tmp_tctx->is_uvar_assigned(i)) return result(e);
}
expr e_s = tmp_tctx->instantiate_uvars_mvars(sr.get_rhs());
if (sr.is_perm() && !is_lt(e_s,e,false)) return result(e);
expr pf = tmp_tctx->instantiate_uvars_mvars(sr.get_proof());
return result(result(e_s,pf));
}
/* Congruence */
result simplifier::congr(result const & r_f, result const & r_arg) {
lean_assert(!r_f.is_none() && !r_arg.is_none());
// theorem congr {A B : Type} {f₁ f₂ : A → B} {a₁ a₂ : A} (H₁ : f₁ = f₂) (H₂ : a₁ = a₂) : f₁ a₁ = f₂ a₂
expr e = mk_app(r_f.get_new(),r_arg.get_new());
if (auto pf = m_app_builder.mk_app(get_congr_name(),r_f.get_proof(),r_arg.get_proof()))
return result(e,*pf);
else
throw blast_exception("failed on [congr] matching",e);
}
result simplifier::congr_fun(result const & r_f, expr const & arg) {
lean_assert(!r_f.is_none());
// theorem congr_fun {A : Type} {B : A → Type} {f g : Π x, B x} (H : f = g) (a : A) : f a = g a
expr e = mk_app(r_f.get_new(),arg);
if (auto pf = m_app_builder.mk_app(get_congr_fun_name(),r_f.get_proof(),arg))
return result(e,*pf);
else
throw blast_exception("failed on [congr_fun] matching",e);
}
result simplifier::congr_arg(expr const & f, result const & r_arg) {
lean_assert(!r_arg.is_none());
// theorem congr_arg {A B : Type} {a₁ a₂ : A} (f : A → B) : a₁ = a₂ → f a₁ = f a₂
expr e = mk_app(f,r_arg.get_new());
if (auto pf = m_app_builder.mk_app(get_congr_arg_name(),f,r_arg.get_proof()))
return result(e,*pf);
else
throw blast_exception("failed on [congr_arg] matching",e);
}
result simplifier::congr_funs(result const & r_f, buffer<expr> const & args) {
lean_assert(!r_f.is_none());
// congr_fun : ∀ {A : Type} {B : A → Type} {f g : Π (x : A), B x}, f = g → (∀ (a : A), f a = g a)
expr e = r_f.get_new();
expr pf = r_f.get_proof();
for (unsigned i = 0; i < args.size(); ++i) {
e = mk_app(e,args[i]);
auto p = m_app_builder.mk_app(get_congr_fun_name(),pf,args[i]);
if (p) pf = *p;
else throw blast_exception("failed on [congr_fun] matching",e);
}
return result(e,pf);
}
result simplifier::try_congrs(expr const & e) {
simp_rule_set const * sr = get_simp_rule_sets(env()).find(m_rel);
if (!sr) return result(e);
list<congr_rule> const * crs = sr->find_congr(e);
if (!crs) return result(e);
result r(e);
for_each(*crs,[&](congr_rule const & cr) {
if (!r.is_none()) return;
r = try_congr(e,cr);
});
return r;
}
result simplifier::try_congr(expr const & e, congr_rule const & cr) {
blast_tmp_type_context tmp_tctx(cr.get_num_umeta(),cr.get_num_emeta());
if (!tmp_tctx->is_def_eq(e,cr.get_lhs())) return result(e);
/* First, iterate over the congruence hypotheses */
bool failed = false;
bool simplified = false;
list<expr> const & congr_hyps = cr.get_congr_hyps();
for_each(congr_hyps,[&](expr const & m) {
if (failed) return;
buffer<expr> ls;
expr m_type = tmp_tctx->infer(m);
while (is_pi(m_type)) {
expr d = instantiate_rev(binding_domain(m_type), ls.size(), ls.data());
expr l = tmp_tctx->mk_tmp_local(d,binding_info(e));
ls.push_back(l);
m_type = instantiate(binding_body(m_type),l);
}
expr h_rel, h_lhs, h_rhs;
bool valid = is_simp_relation(env(), m_type, h_rel, h_lhs, h_rhs) && is_constant(h_rel);
lean_assert(valid);
{
flet<name> set_name(m_rel,const_name(h_rel));
flet<list<expr>> set_local_ctx(m_local_ctx,to_list(ls));
h_lhs = tmp_tctx->instantiate_uvars_mvars(h_lhs);
result r_congr_hyp = simplify(h_lhs);
expr hyp;
if (r_congr_hyp.is_none()) {
hyp = finalize(r_congr_hyp).get_proof();
}
else {
hyp = r_congr_hyp.get_proof();
simplified = true;
}
hyp = Fun(ls,hyp);
if (!tmp_tctx->is_def_eq(m,hyp)) failed = true;
}
});
if (failed || !simplified) return result(e);
/* Traverse metavariables backwards, proving or synthesizing the rest */
for (int i = cr.get_num_emeta() - 1; i >= 0; --i) {
expr const & m = cr.get_emeta(i);
bool is_instance = cr.is_instance(i);
if (is_instance) {
expr type = tmp_tctx->instantiate_uvars_mvars(tmp_tctx->infer(m));
if (auto v = tmp_tctx->mk_class_instance(type)) {
if (!tmp_tctx->force_assign(m, *v))
return result(e);
} else {
return result(e);
}
}
if (tmp_tctx->is_mvar_assigned(i)) continue;
if (tmp_tctx->is_prop(tmp_tctx->infer(m))) {
// TODO try to prove
return result(e);
}
/* We fail if there is a meta variable that we still cannot assign */
return result(e);
}
for (unsigned i = 0; i < cr.get_num_umeta(); i++) {
if (!tmp_tctx->is_uvar_assigned(i)) return result(e);
}
expr e_s = tmp_tctx->instantiate_uvars_mvars(cr.get_rhs());
expr pf = tmp_tctx->instantiate_uvars_mvars(cr.get_proof());
return result(e_s,pf);
}
/* Setup and teardown */
void initialize_simplifier() {
g_simplify_max_steps = new name{"simplify", "max_steps"};
g_simplify_top_down = new name{"simplify", "top_down"};
g_simplify_exhaustive = new name{"simplify", "exhaustive"};
g_simplify_memoize = new name{"simplify", "memoize"};
g_simplify_contextual = new name{"simplify", "contextual"};
g_simplify_expand_macros = new name{"simplify", "expand_macros"};
g_simplify_trace = new name{"simplify", "trace"};
register_unsigned_option(*g_simplify_max_steps, LEAN_DEFAULT_SIMPLIFY_MAX_STEPS,
"(simplify) max allowed steps in simplification");
register_bool_option(*g_simplify_top_down, LEAN_DEFAULT_SIMPLIFY_TOP_DOWN,
"(simplify) use top-down rewriting instead of bottom-up");
register_bool_option(*g_simplify_exhaustive, LEAN_DEFAULT_SIMPLIFY_EXHAUSTIVE,
"(simplify) rewrite exhaustively");
register_bool_option(*g_simplify_memoize, LEAN_DEFAULT_SIMPLIFY_MEMOIZE,
"(simplify) memoize simplifications");
register_bool_option(*g_simplify_contextual, LEAN_DEFAULT_SIMPLIFY_CONTEXTUAL,
"(simplify) use contextual simplification");
register_bool_option(*g_simplify_expand_macros, LEAN_DEFAULT_SIMPLIFY_EXPAND_MACROS,
"(simplify) expand macros");
register_bool_option(*g_simplify_trace, LEAN_DEFAULT_SIMPLIFY_TRACE,
"(simplify) trace");
}
void finalize_simplifier() {
delete g_simplify_trace;
delete g_simplify_expand_macros;
delete g_simplify_contextual;
delete g_simplify_memoize;
delete g_simplify_exhaustive;
delete g_simplify_top_down;
delete g_simplify_max_steps;
}
/* Entry point */
result simplify(branch const & b, name const & rel, expr const & e) {
return simplifier(b,rel)(e);
}
}}