97 lines
2.7 KiB
C++
97 lines
2.7 KiB
C++
/*
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Copyright (c) 2013 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 "util/name_set.h"
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#include "kernel/context.h"
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#include "kernel/instantiate.h"
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#include "kernel/environment.h"
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#include "kernel/free_vars.h"
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#include "kernel/replace.h"
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#include "library/update_expr.h"
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namespace lean {
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bool is_head_beta(expr const & t) {
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return is_app(t) && is_lambda(arg(t, 0));
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}
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expr head_beta_reduce(expr const & t) {
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if (!is_head_beta(t)) {
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return t;
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} else {
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unsigned num = num_args(t);
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unsigned num1 = num - 1;
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expr const * f = &arg(t, 0);
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lean_assert(is_lambda(*f));
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unsigned m = 1;
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while (is_lambda(abst_body(*f)) && m < num1) {
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f = &abst_body(*f);
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m++;
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}
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lean_assert(m <= num1);
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expr r = instantiate(abst_body(*f), m, &arg(t, 1));
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if (m == num1) {
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return r;
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} else {
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buffer<expr> args;
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args.push_back(r);
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m++;
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for (; m < num; m++)
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args.push_back(arg(t, m));
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return mk_app(args.size(), args.data());
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}
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}
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}
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expr beta_reduce(expr t) {
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auto f = [=](expr const & m, unsigned) -> expr {
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if (is_head_beta(m))
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return head_beta_reduce(m);
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else
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return m;
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};
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while (true) {
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expr new_t = replace_fn<decltype(f)>(f)(t);
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if (new_t == t)
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return new_t;
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else
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t = new_t;
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}
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}
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expr head_reduce(expr const & t, environment const & e, context const & c, name_set const * defs) {
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if (is_head_beta(t)) {
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return head_beta_reduce(t);
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} else if (is_app(t)) {
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expr f = arg(t, 0);
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if (is_head_beta(f) || is_let(f) || is_constant(f) || is_var(f)) {
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expr new_f = head_reduce(f, e, c, defs);
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if (!is_eqp(f, new_f))
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return update_app(t, 0, new_f);
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else
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return t;
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} else {
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return t;
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}
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} else if (is_var(t)) {
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auto p = lookup_ext(c, var_idx(t));
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context_entry const & ce = p.first;
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if (ce.get_body()) {
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return lift_free_vars(ce.get_body(), c.size() - p.second.size());
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} else {
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return t;
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}
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} else if (is_let(t)) {
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return instantiate(let_body(t), let_value(t));
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} else if (is_constant(t)) {
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name const & n = const_name(t);
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if (defs == nullptr || defs->find(n) != defs->end()) {
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object const & obj = e.find_object(n);
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if (obj && obj.is_definition() && !obj.is_opaque())
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return obj.get_value();
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}
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}
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return t;
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}
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}
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