bool is_recursive_rec_app(environment const & env, expr const & e) {
buffer<expr> args;
name_generator ngen;
expr const & f = get_app_args(e, args);
if (!is_constant(f))
return false;
auto I_name = inductive::is_elim_rule(env, const_name(f));
if (!I_name || !is_recursive_datatype(env, *I_name) || is_inductive_predicate(env, *I_name))
return false;
unsigned nparams = *inductive::get_num_params(env, *I_name);
unsigned nminors = *inductive::get_num_minor_premises(env, *I_name);
unsigned ntypeformers = *inductive::get_num_type_formers(env, *I_name);
buffer<buffer<bool>> is_rec_arg;
get_rec_args(env, *I_name, is_rec_arg);
for (unsigned i = nparams + ntypeformers, j = 0; i < nparams + ntypeformers + nminors; i++, j++) {
buffer<bool> const & minor_is_rec_arg = is_rec_arg[j];
expr minor = args[i];
buffer<expr> minor_ctx;
expr minor_body = fun_to_telescope(ngen, minor, minor_ctx, optional<binder_info>());
unsigned sz = std::min(minor_is_rec_arg.size(), minor_ctx.size());
if (find(minor_body, [&](expr const & e, unsigned) {
if (!is_local(e))
return false;
for (unsigned k = 0; k < sz; k++) {
if (minor_is_rec_arg[k] && mlocal_name(e) == mlocal_name(minor_ctx[k]))
return true;
}
return false;
}))
return false;
}
return true;
}
expr visit_cases_on(name const & fn, buffer<expr> & args) {
name const & I_name = fn.get_prefix();
if (is_inductive_predicate(env(), I_name))
throw exception(sstream() << "code generation failed, inductive predicate '" << I_name << "' is not supported");
bool is_builtin = is_vm_builtin_function(fn);
buffer<name> cnames;
get_intro_rule_names(env(), I_name, cnames);
lean_assert(args.size() >= cnames.size() + 1);
if (args.size() > cnames.size() + 1)
distribute_extra_args_over_minors(I_name, cnames, args);
lean_assert(args.size() == cnames.size() + 1);
/* Process major premise */
args[0] = visit(args[0]);
unsigned num_reachable = 0;
optional<expr> reachable_case;
/* Process minor premises */
for (unsigned i = 0; i < cnames.size(); i++) {
buffer<bool> rel_fields;
get_constructor_info(cnames[i], rel_fields);
auto p = visit_minor_premise(args[i+1], rel_fields);
expr new_minor = p.first;
if (i == 0 && has_trivial_structure(I_name, rel_fields)) {
/* Optimization for an inductive datatype that has a single constructor with only one relevant field */
return beta_reduce(mk_app(new_minor, args[0]));
}
args[i+1] = new_minor;
if (!p.second) {
num_reachable++;
reachable_case = p.first;
}
}
if (num_reachable == 0) {
return mk_unreachable_expr();
} else if (num_reachable == 1 && !is_builtin) {
/* Use _cases.1 */
return mk_app(mk_cases(1), args[0], *reachable_case);
} else if (is_builtin) {
return mk_app(mk_constant(fn), args);
} else {
return mk_app(mk_cases(cnames.size()), args);
}
}
static environment mk_below(environment const & env, name const & n, bool ibelow) {
if (!is_recursive_datatype(env, n))
return env;
if (is_inductive_predicate(env, n))
return env;
inductive::inductive_decls decls = *inductive::is_inductive_decl(env, n);
type_checker tc(env);
name_generator ngen;
unsigned nparams = std::get<1>(decls);
declaration ind_decl = env.get(n);
declaration rec_decl = env.get(inductive::get_elim_name(n));
unsigned nindices = *inductive::get_num_indices(env, n);
unsigned nminors = *inductive::get_num_minor_premises(env, n);
unsigned ntypeformers = length(std::get<2>(decls));
level_param_names lps = rec_decl.get_univ_params();
bool is_reflexive = is_reflexive_datatype(tc, n);
level lvl = mk_param_univ(head(lps));
levels lvls = param_names_to_levels(tail(lps));
level_param_names blvls; // universe level parameters of ibelow/below
level rlvl; // universe level of the resultant type
// The arguments of below (ibelow) are the ones in the recursor - minor premises.
// The universe we map to is also different (l+1 for below of reflexive types) and (0 fo ibelow).
expr ref_type;
expr Type_result;
if (ibelow) {
// we are eliminating to Prop
blvls = tail(lps);
rlvl = mk_level_zero();
ref_type = instantiate_univ_param(rec_decl.get_type(), param_id(lvl), mk_level_zero());
} else if (is_reflexive) {
blvls = lps;
rlvl = get_datatype_level(ind_decl.get_type());
// if rlvl is of the form (max 1 l), then rlvl <- l
if (is_max(rlvl) && is_one(max_lhs(rlvl)))
rlvl = max_rhs(rlvl);
rlvl = mk_max(mk_succ(lvl), rlvl);
ref_type = instantiate_univ_param(rec_decl.get_type(), param_id(lvl), mk_succ(lvl));
} else {
// we can simplify the universe levels for non-reflexive datatypes
blvls = lps;
rlvl = mk_max(mk_level_one(), lvl);
ref_type = rec_decl.get_type();
}
Type_result = mk_sort(rlvl);
buffer<expr> ref_args;
to_telescope(ngen, ref_type, ref_args);
if (ref_args.size() != nparams + ntypeformers + nminors + nindices + 1)
throw_corrupted(n);
// args contains the below/ibelow arguments
buffer<expr> args;
buffer<name> typeformer_names;
// add parameters and typeformers
for (unsigned i = 0; i < nparams; i++)
args.push_back(ref_args[i]);
for (unsigned i = nparams; i < nparams + ntypeformers; i++) {
args.push_back(ref_args[i]);
typeformer_names.push_back(mlocal_name(ref_args[i]));
}
// we ignore minor premises in below/ibelow
for (unsigned i = nparams + ntypeformers + nminors; i < ref_args.size(); i++)
args.push_back(ref_args[i]);
// We define below/ibelow using the recursor for this type
levels rec_lvls = cons(mk_succ(rlvl), lvls);
expr rec = mk_constant(rec_decl.get_name(), rec_lvls);
for (unsigned i = 0; i < nparams; i++)
rec = mk_app(rec, args[i]);
// add type formers
for (unsigned i = nparams; i < nparams + ntypeformers; i++) {
buffer<expr> targs;
to_telescope(ngen, mlocal_type(args[i]), targs);
rec = mk_app(rec, Fun(targs, Type_result));
}
// add minor premises
for (unsigned i = nparams + ntypeformers; i < nparams + ntypeformers + nminors; i++) {
expr minor = ref_args[i];
expr minor_type = mlocal_type(minor);
buffer<expr> minor_args;
minor_type = to_telescope(ngen, minor_type, minor_args);
buffer<expr> prod_pairs;
for (expr & minor_arg : minor_args) {
buffer<expr> minor_arg_args;
expr minor_arg_type = to_telescope(tc, mlocal_type(minor_arg), minor_arg_args);
if (is_typeformer_app(typeformer_names, minor_arg_type)) {
expr fst = mlocal_type(minor_arg);
minor_arg = update_mlocal(minor_arg, Pi(minor_arg_args, Type_result));
expr snd = Pi(minor_arg_args, mk_app(minor_arg, minor_arg_args));
prod_pairs.push_back(mk_prod(tc, fst, snd, ibelow));
}
}
expr new_arg = foldr([&](expr const & a, expr const & b) { return mk_prod(tc, a, b, ibelow); },
[&]() { return mk_unit(rlvl, ibelow); },
prod_pairs.size(), prod_pairs.data());
rec = mk_app(rec, Fun(minor_args, new_arg));
}
// add indices and major premise
for (unsigned i = nparams + ntypeformers; i < args.size(); i++) {
rec = mk_app(rec, args[i]);
}
name below_name = ibelow ? name{n, "ibelow"} : name{n, "below"};
expr below_type = Pi(args, Type_result);
expr below_value = Fun(args, rec);
bool use_conv_opt = true;
declaration new_d = mk_definition(env, below_name, blvls, below_type, below_value,
use_conv_opt);
environment new_env = module::add(env, check(env, new_d));
new_env = set_reducible(new_env, below_name, reducible_status::Reducible);
if (!ibelow)
new_env = add_unfold_hint(new_env, below_name, nparams + nindices + ntypeformers);
return add_protected(new_env, below_name);
}
static environment mk_brec_on(environment const & env, name const & n, bool ind) {
if (!is_recursive_datatype(env, n))
return env;
if (is_inductive_predicate(env, n))
return env;
inductive::inductive_decls decls = *inductive::is_inductive_decl(env, n);
type_checker tc(env);
name_generator ngen;
unsigned nparams = std::get<1>(decls);
declaration ind_decl = env.get(n);
declaration rec_decl = env.get(inductive::get_elim_name(n));
// declaration below_decl = env.get(name(n, ind ? "ibelow" : "below"));
unsigned nindices = *inductive::get_num_indices(env, n);
unsigned nminors = *inductive::get_num_minor_premises(env, n);
unsigned ntypeformers = length(std::get<2>(decls));
level_param_names lps = rec_decl.get_univ_params();
bool is_reflexive = is_reflexive_datatype(tc, n);
level lvl = mk_param_univ(head(lps));
levels lvls = param_names_to_levels(tail(lps));
level rlvl;
level_param_names blps;
levels blvls; // universe level parameters of brec_on/binduction_on
// The arguments of brec_on (binduction_on) are the ones in the recursor - minor premises.
// The universe we map to is also different (l+1 for below of reflexive types) and (0 fo ibelow).
expr ref_type;
if (ind) {
// we are eliminating to Prop
blps = tail(lps);
blvls = lvls;
rlvl = mk_level_zero();
ref_type = instantiate_univ_param(rec_decl.get_type(), param_id(lvl), mk_level_zero());
} else if (is_reflexive) {
blps = lps;
blvls = cons(lvl, lvls);
rlvl = get_datatype_level(ind_decl.get_type());
// if rlvl is of the form (max 1 l), then rlvl <- l
if (is_max(rlvl) && is_one(max_lhs(rlvl)))
rlvl = max_rhs(rlvl);
rlvl = mk_max(mk_succ(lvl), rlvl);
// inner_prod, inner_prod_intro, pr1, pr2 do not use the same universe levels for
// reflective datatypes.
ref_type = instantiate_univ_param(rec_decl.get_type(), param_id(lvl), mk_succ(lvl));
} else {
// we can simplify the universe levels for non-reflexive datatypes
blps = lps;
blvls = cons(lvl, lvls);
rlvl = mk_max(mk_level_one(), lvl);
ref_type = rec_decl.get_type();
}
buffer<expr> ref_args;
to_telescope(ngen, ref_type, ref_args);
if (ref_args.size() != nparams + ntypeformers + nminors + nindices + 1)
throw_corrupted(n);
// args contains the brec_on/binduction_on arguments
buffer<expr> args;
buffer<name> typeformer_names;
// add parameters and typeformers
for (unsigned i = 0; i < nparams; i++)
args.push_back(ref_args[i]);
for (unsigned i = nparams; i < nparams + ntypeformers; i++) {
args.push_back(ref_args[i]);
typeformer_names.push_back(mlocal_name(ref_args[i]));
}
// add indices and major premise
for (unsigned i = nparams + ntypeformers + nminors; i < ref_args.size(); i++)
args.push_back(ref_args[i]);
// create below terms (one per datatype)
// (below.{lvls} params type-formers)
// Remark: it also creates the result type
buffer<expr> belows;
expr result_type;
unsigned k = 0;
for (auto const & decl : std::get<2>(decls)) {
name const & n1 = inductive::inductive_decl_name(decl);
if (n1 == n) {
result_type = ref_args[nparams + k];
for (unsigned i = nparams + ntypeformers + nminors; i < ref_args.size(); i++)
result_type = mk_app(result_type, ref_args[i]);
}
k++;
name bname = name(n1, ind ? "ibelow" : "below");
expr below = mk_constant(bname, blvls);
for (unsigned i = 0; i < nparams; i++)
below = mk_app(below, ref_args[i]);
for (unsigned i = nparams; i < nparams + ntypeformers; i++)
below = mk_app(below, ref_args[i]);
belows.push_back(below);
}
// create functionals (one for each type former)
// Pi idxs t, below idxs t -> C idxs t
buffer<expr> Fs;
name F_name("F");
for (unsigned i = nparams, j = 0; i < nparams + ntypeformers; i++, j++) {
expr const & C = ref_args[i];
buffer<expr> F_args;
to_telescope(ngen, mlocal_type(C), F_args);
expr F_result = mk_app(C, F_args);
expr F_below = mk_app(belows[j], F_args);
F_args.push_back(mk_local(ngen.next(), "f", F_below, binder_info()));
expr F_type = Pi(F_args, F_result);
expr F = mk_local(ngen.next(), F_name.append_after(j+1), F_type, binder_info());
Fs.push_back(F);
args.push_back(F);
}
// We define brec_on/binduction_on using the recursor for this type
levels rec_lvls = cons(rlvl, lvls);
expr rec = mk_constant(rec_decl.get_name(), rec_lvls);
// add parameters to rec
for (unsigned i = 0; i < nparams; i++)
rec = mk_app(rec, ref_args[i]);
// add type formers to rec
// Pi indices t, prod (C ... t) (below ... t)
for (unsigned i = nparams, j = 0; i < nparams + ntypeformers; i++, j++) {
expr const & C = ref_args[i];
buffer<expr> C_args;
to_telescope(ngen, mlocal_type(C), C_args);
expr C_t = mk_app(C, C_args);
expr below_t = mk_app(belows[j], C_args);
expr prod = mk_prod(tc, C_t, below_t, ind);
rec = mk_app(rec, Fun(C_args, prod));
}
// add minor premises to rec
for (unsigned i = nparams + ntypeformers, j = 0; i < nparams + ntypeformers + nminors; i++, j++) {
expr minor = ref_args[i];
expr minor_type = mlocal_type(minor);
buffer<expr> minor_args;
minor_type = to_telescope(ngen, minor_type, minor_args);
buffer<expr> pairs;
for (expr & minor_arg : minor_args) {
buffer<expr> minor_arg_args;
expr minor_arg_type = to_telescope(tc, mlocal_type(minor_arg), minor_arg_args);
if (auto k = is_typeformer_app(typeformer_names, minor_arg_type)) {
buffer<expr> C_args;
get_app_args(minor_arg_type, C_args);
expr new_minor_arg_type = mk_prod(tc, minor_arg_type, mk_app(belows[*k], C_args), ind);
minor_arg = update_mlocal(minor_arg, Pi(minor_arg_args, new_minor_arg_type));
if (minor_arg_args.empty()) {
pairs.push_back(minor_arg);
} else {
expr r = mk_app(minor_arg, minor_arg_args);
expr r_1 = Fun(minor_arg_args, mk_pr1(tc, r, ind));
expr r_2 = Fun(minor_arg_args, mk_pr2(tc, r, ind));
pairs.push_back(mk_pair(tc, r_1, r_2, ind));
}
}
}
expr b = foldr([&](expr const & a, expr const & b) { return mk_pair(tc, a, b, ind); },
[&]() { return mk_unit_mk(rlvl, ind); },
pairs.size(), pairs.data());
unsigned F_idx = *is_typeformer_app(typeformer_names, minor_type);
expr F = Fs[F_idx];
buffer<expr> F_args;
get_app_args(minor_type, F_args);
F_args.push_back(b);
expr new_arg = mk_pair(tc, mk_app(F, F_args), b, ind);
rec = mk_app(rec, Fun(minor_args, new_arg));
}
// add indices and major to rec
for (unsigned i = nparams + ntypeformers + nminors; i < ref_args.size(); i++)
rec = mk_app(rec, ref_args[i]);
name brec_on_name = name(n, ind ? "binduction_on" : "brec_on");
expr brec_on_type = Pi(args, result_type);
expr brec_on_value = Fun(args, mk_pr1(tc, rec, ind));
bool use_conv_opt = true;
declaration new_d = mk_definition(env, brec_on_name, blps, brec_on_type, brec_on_value,
use_conv_opt);
environment new_env = module::add(env, check(env, new_d));
new_env = set_reducible(new_env, brec_on_name, reducible_status::Reducible);
if (!ind)
new_env = add_unfold_hint(new_env, brec_on_name, nparams + nindices + ntypeformers);
return add_protected(new_env, brec_on_name);
}
optional<environment> mk_no_confusion_type(environment const & env, name const & n) {
optional<inductive::inductive_decls> decls = inductive::is_inductive_decl(env, n);
if (!decls)
throw exception(sstream() << "error in 'no_confusion' generation, '" << n << "' is not an inductive datatype");
if (is_inductive_predicate(env, n))
return optional<environment>(); // type is a proposition
name_generator ngen;
unsigned nparams = std::get<1>(*decls);
declaration ind_decl = env.get(n);
declaration cases_decl = env.get(name(n, "cases_on"));
level_param_names lps = cases_decl.get_univ_params();
level rlvl = mk_param_univ(head(lps));
levels ilvls = param_names_to_levels(tail(lps));
if (length(ilvls) != length(ind_decl.get_univ_params()))
return optional<environment>(); // type does not have only a restricted eliminator
expr ind_type = instantiate_type_univ_params(ind_decl, ilvls);
name eq_name("eq");
name heq_name("heq");
// All inductive datatype parameters and indices are arguments
buffer<expr> args;
ind_type = to_telescope(ngen, ind_type, args, some(mk_implicit_binder_info()));
if (!is_sort(ind_type) || args.size() < nparams)
throw_corrupted(n);
lean_assert(!(env.impredicative() && is_zero(sort_level(ind_type))));
unsigned nindices = args.size() - nparams;
// Create inductive datatype
expr I = mk_app(mk_constant(n, ilvls), args);
// Add (P : Type)
expr P = mk_local(ngen.next(), "P", mk_sort(rlvl), binder_info());
args.push_back(P);
// add v1 and v2 elements of the inductive type
expr v1 = mk_local(ngen.next(), "v1", I, binder_info());
expr v2 = mk_local(ngen.next(), "v2", I, binder_info());
args.push_back(v1);
args.push_back(v2);
expr R = mk_sort(rlvl);
name no_confusion_type_name{n, "no_confusion_type"};
expr no_confusion_type_type = Pi(args, R);
// Create type former
buffer<expr> type_former_args;
for (unsigned i = nparams; i < nparams + nindices; i++)
type_former_args.push_back(args[i]);
type_former_args.push_back(v1);
expr type_former = Fun(type_former_args, R);
// Create cases_on
levels clvls = levels(mk_succ(rlvl), ilvls);
expr cases_on = mk_app(mk_app(mk_constant(cases_decl.get_name(), clvls), nparams, args.data()), type_former);
cases_on = mk_app(cases_on, nindices, args.data() + nparams);
expr cases_on1 = mk_app(cases_on, v1);
expr cases_on2 = mk_app(cases_on, v2);
type_checker tc(env);
expr t1 = tc.infer(cases_on1).first;
expr t2 = tc.infer(cases_on2).first;
buffer<expr> outer_cases_on_args;
unsigned idx1 = 0;
while (is_pi(t1)) {
buffer<expr> minor1_args;
expr minor1 = to_telescope(tc, binding_domain(t1), minor1_args);
expr curr_t2 = t2;
buffer<expr> inner_cases_on_args;
unsigned idx2 = 0;
while (is_pi(curr_t2)) {
buffer<expr> minor2_args;
expr minor2 = to_telescope(tc, binding_domain(curr_t2), minor2_args);
if (idx1 != idx2) {
// infeasible case, constructors do not match
inner_cases_on_args.push_back(Fun(minor2_args, P));
} else {
if (minor1_args.size() != minor2_args.size())
throw_corrupted(n);
buffer<expr> rtype_hyp;
// add equalities
for (unsigned i = 0; i < minor1_args.size(); i++) {
expr lhs = minor1_args[i];
expr rhs = minor2_args[i];
expr lhs_type = mlocal_type(lhs);
expr rhs_type = mlocal_type(rhs);
level l = sort_level(tc.ensure_type(lhs_type).first);
expr h_type;
if (tc.is_def_eq(lhs_type, rhs_type).first) {
h_type = mk_app(mk_constant(eq_name, to_list(l)), lhs_type, lhs, rhs);
} else {
h_type = mk_app(mk_constant(heq_name, to_list(l)), lhs_type, lhs, rhs_type, rhs);
}
rtype_hyp.push_back(mk_local(ngen.next(), local_pp_name(lhs).append_after("_eq"), h_type, binder_info()));
}
inner_cases_on_args.push_back(Fun(minor2_args, mk_arrow(Pi(rtype_hyp, P), P)));
}
idx2++;
curr_t2 = binding_body(curr_t2);
}
outer_cases_on_args.push_back(Fun(minor1_args, mk_app(cases_on2, inner_cases_on_args)));
idx1++;
t1 = binding_body(t1);
}
expr no_confusion_type_value = Fun(args, mk_app(cases_on1, outer_cases_on_args));
bool opaque = false;
bool use_conv_opt = true;
declaration new_d = mk_definition(env, no_confusion_type_name, lps, no_confusion_type_type, no_confusion_type_value,
opaque, ind_decl.get_module_idx(), use_conv_opt);
environment new_env = module::add(env, check(env, new_d));
return some(add_protected(new_env, no_confusion_type_name));
}