lean2/src/kernel/instantiate.cpp
2015-01-28 17:22:18 -08:00

218 lines
7.7 KiB
C++

/*
Copyright (c) 2013 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Author: Leonardo de Moura
*/
#include <algorithm>
#include <limits>
#include <vector>
#include "kernel/free_vars.h"
#include "kernel/replace_fn.h"
#include "kernel/declaration.h"
#include "kernel/instantiate.h"
#ifndef LEAN_INST_UNIV_CACHE_SIZE
#define LEAN_INST_UNIV_CACHE_SIZE 1023
#endif
namespace lean {
template<bool rev>
struct instantiate_easy_fn {
unsigned n;
expr const * subst;
instantiate_easy_fn(unsigned _n, expr const * _subst):n(_n), subst(_subst) {}
optional<expr> operator()(expr const & a, bool app) const {
if (closed(a))
return some_expr(a);
if (is_var(a) && var_idx(a) < n)
return some_expr(subst[rev ? n - var_idx(a) - 1 : var_idx(a)]);
if (app && is_app(a))
if (auto new_a = operator()(app_arg(a), false))
if (auto new_f = operator()(app_fn(a), true))
return some_expr(mk_app(*new_f, *new_a, a.get_tag()));
return none_expr();
}
};
expr instantiate(expr const & a, unsigned s, unsigned n, expr const * subst) {
if (s >= get_free_var_range(a) || n == 0)
return a;
if (s == 0)
if (auto r = instantiate_easy_fn<false>(n, subst)(a, true))
return *r;
return replace(a, [=](expr const & m, unsigned offset) -> optional<expr> {
unsigned s1 = s + offset;
if (s1 < s)
return some_expr(m); // overflow, vidx can't be >= max unsigned
if (s1 >= get_free_var_range(m))
return some_expr(m); // expression m does not contain free variables with idx >= s1
if (is_var(m)) {
unsigned vidx = var_idx(m);
if (vidx >= s1) {
unsigned h = s1 + n;
if (h < s1 /* overflow, h is bigger than any vidx */ || vidx < h) {
return some_expr(lift_free_vars(subst[vidx - s1], offset));
} else {
return some_expr(mk_var(vidx - n));
}
}
}
return none_expr();
});
}
expr instantiate(expr const & e, unsigned n, expr const * s) { return instantiate(e, 0, n, s); }
expr instantiate(expr const & e, std::initializer_list<expr> const & l) { return instantiate(e, l.size(), l.begin()); }
expr instantiate(expr const & e, unsigned i, expr const & s) { return instantiate(e, i, 1, &s); }
expr instantiate(expr const & e, expr const & s) { return instantiate(e, 0, s); }
expr instantiate_rev(expr const & a, unsigned n, expr const * subst) {
if (closed(a))
return a;
if (auto r = instantiate_easy_fn<true>(n, subst)(a, true))
return *r;
return replace(a, [=](expr const & m, unsigned offset) -> optional<expr> {
if (offset >= get_free_var_range(m))
return some_expr(m); // expression m does not contain free variables with idx >= offset
if (is_var(m)) {
unsigned vidx = var_idx(m);
if (vidx >= offset) {
unsigned h = offset + n;
if (h < offset /* overflow, h is bigger than any vidx */ || vidx < h) {
return some_expr(lift_free_vars(subst[n - (vidx - offset) - 1], offset));
} else {
return some_expr(mk_var(vidx - n));
}
}
}
return none_expr();
});
}
bool is_head_beta(expr const & t) {
return is_app(t) && is_lambda(get_app_fn(t));
}
expr apply_beta(expr f, unsigned num_args, expr const * args) {
if (num_args == 0) {
return f;
} else if (!is_lambda(f)) {
return mk_rev_app(f, num_args, args);
} else {
unsigned m = 1;
while (is_lambda(binding_body(f)) && m < num_args) {
f = binding_body(f);
m++;
}
lean_assert(m <= num_args);
return mk_rev_app(instantiate(binding_body(f), m, args + (num_args - m)), num_args - m, args);
}
}
expr head_beta_reduce(expr const & t) {
if (!is_head_beta(t)) {
return t;
} else {
buffer<expr> args;
expr const & f = get_app_rev_args(t, args);
lean_assert(is_lambda(f));
return apply_beta(f, args.size(), args.data());
}
}
expr beta_reduce(expr t) {
bool reduced = false;
auto f = [&](expr const & m, unsigned) -> optional<expr> {
if (is_head_beta(m)) {
reduced = true;
return some_expr(head_beta_reduce(m));
} else if (is_local(m) || is_metavar(m)) {
return some_expr(m); // do not simplify local constants and metavariables types.
} else {
return none_expr();
}
};
while (true) {
reduced = false;
expr new_t = replace(t, f);
if (!reduced)
return new_t;
else
t = new_t;
}
}
expr instantiate_univ_params(expr const & e, level_param_names const & ps, levels const & ls) {
if (!has_param_univ(e))
return e;
return replace(e, [&](expr const & e) -> optional<expr> {
if (!has_param_univ(e))
return some_expr(e);
if (is_constant(e)) {
return some_expr(update_constant(e, map_reuse(const_levels(e),
[&](level const & l) { return instantiate(l, ps, ls); },
[](level const & l1, level const & l2) { return is_eqp(l1, l2); })));
} else if (is_sort(e)) {
return some_expr(update_sort(e, instantiate(sort_level(e), ps, ls)));
} else {
return none_expr();
}
});
}
class instantiate_univ_cache {
typedef std::tuple<declaration, levels, expr> entry;
std::vector<optional<entry>> m_cache;
public:
instantiate_univ_cache() {
m_cache.resize(LEAN_INST_UNIV_CACHE_SIZE);
}
optional<expr> is_cached(declaration const & d, levels const & ls) {
unsigned idx = d.get_name().hash() % LEAN_INST_UNIV_CACHE_SIZE;
if (auto it = m_cache[idx]) {
declaration d_c; levels ls_c; expr r_c;
std::tie(d_c, ls_c, r_c) = *it;
if (!is_eqp(d_c, d))
return none_expr();
if (ls == ls_c)
return some_expr(r_c);
else
return none_expr();
}
return none_expr();
}
void save(declaration const & d, levels const & ls, expr const & r) {
unsigned idx = d.get_name().hash() % LEAN_INST_UNIV_CACHE_SIZE;
m_cache[idx] = entry(d, ls, r);
}
};
MK_THREAD_LOCAL_GET_DEF(instantiate_univ_cache, get_type_univ_cache);
MK_THREAD_LOCAL_GET_DEF(instantiate_univ_cache, get_value_univ_cache);
expr instantiate_type_univ_params(declaration const & d, levels const & ls) {
lean_assert(d.get_num_univ_params() == length(ls));
if (is_nil(ls) || !has_param_univ(d.get_type()))
return d.get_type();
instantiate_univ_cache & cache = get_type_univ_cache();
if (auto r = cache.is_cached(d, ls))
return *r;
expr r = instantiate_univ_params(d.get_type(), d.get_univ_params(), ls);
cache.save(d, ls, r);
return r;
}
expr instantiate_value_univ_params(declaration const & d, levels const & ls) {
lean_assert(d.get_num_univ_params() == length(ls));
if (is_nil(ls) || !has_param_univ(d.get_value()))
return d.get_value();
instantiate_univ_cache & cache = get_value_univ_cache();
if (auto r = cache.is_cached(d, ls))
return *r;
expr r = instantiate_univ_params(d.get_value(), d.get_univ_params(), ls);
cache.save(d, ls, r);
return r;
}
}