238 lines
6.6 KiB
C++
238 lines
6.6 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 <limits>
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#include "util/exception.h"
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#include "kernel/metavar.h"
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#include "kernel/replace.h"
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#include "kernel/free_vars.h"
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#include "kernel/instantiate.h"
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#include "kernel/occurs.h"
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#include "kernel/for_each.h"
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namespace lean {
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void metavar_env::inc_timestamp() {
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if (m_timestamp == std::numeric_limits<unsigned>::max()) {
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// This should not happen in real examples. We add it just to be safe.
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throw exception("metavar_env timestamp overflow");
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}
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m_timestamp++;
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}
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metavar_env::metavar_env():m_timestamp(0) {}
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expr metavar_env::mk_metavar(expr const & type, context const & ctx) {
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inc_timestamp();
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unsigned midx = m_env.size();
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m_env.push_back(data(type, ctx));
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return ::lean::mk_metavar(midx);
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}
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expr metavar_env::mk_metavar(context const & ctx) {
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return mk_metavar(expr(), ctx);
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}
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bool metavar_env::contains(unsigned midx) const {
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return midx < m_env.size();
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}
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bool metavar_env::is_assigned(unsigned midx) const {
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return m_env[midx].m_subst;
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}
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expr metavar_env::get_subst_core(unsigned midx) const {
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return m_env[midx].m_subst;
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}
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expr metavar_env::get_subst(unsigned midx) const {
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expr r = m_env[midx].m_subst;
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if (r && has_assigned_metavar(r, *this)) {
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r = instantiate_metavars(r, *this);
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expr t = m_env[midx].m_type;
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context ctx = m_env[midx].m_ctx;
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const_cast<metavar_env*>(this)->m_env[midx] = data(r, t, ctx);
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return r;
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} else {
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return r;
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}
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}
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expr metavar_env::get_type(unsigned midx, unification_problems & up) {
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data d = m_env[midx];
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expr t = d.m_type;
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if (t) {
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return t;
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} else {
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t = mk_metavar();
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expr s = d.m_subst;
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m_env[midx] = data(s, t, d.m_ctx);
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if (s)
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up.add_type_of_eq(d.m_ctx, s, t);
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else
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up.add_type_of_eq(d.m_ctx, ::lean::mk_metavar(midx), t);
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return t;
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}
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}
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expr metavar_env::get_type(unsigned midx) const {
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return m_env[midx].m_type;
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}
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void metavar_env::assign(unsigned midx, expr const & v) {
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inc_timestamp();
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lean_assert(!is_assigned(midx));
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data const & d = m_env[midx];
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m_env[midx] = data(v, d.m_type, d.m_ctx);
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}
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context const & metavar_env::get_context(unsigned midx) const {
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return m_env[midx].m_ctx;
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}
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expr instantiate(expr const & s, meta_ctx const & ctx, metavar_env const & env) {
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if (ctx) {
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expr r = instantiate(s, tail(ctx), env);
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meta_entry const & e = head(ctx);
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if (e.is_lift()) {
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return lift_free_vars(r, e.s(), e.n());
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} else {
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lean_assert(e.is_inst());
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return ::lean::instantiate(r, e.s(), instantiate_metavars(e.v(), env));
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}
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} else {
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return s;
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}
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}
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expr metavar_env::get_subst(expr const & m) const {
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expr s = get_subst(metavar_idx(m));
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if (s)
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return instantiate(s, metavar_ctx(m), *this);
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else
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return s;
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}
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expr metavar_env::get_type(expr const & m, unification_problems & up) {
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expr s = get_type(metavar_idx(m), up);
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return instantiate(s, metavar_ctx(m), *this);
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}
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void metavar_env::assign(expr const & m, expr const & t) {
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lean_assert(!metavar_ctx(m));
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assign(metavar_idx(m), t);
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}
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expr instantiate_metavars(expr const & e, metavar_env const & env) {
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if (!has_metavar(e)) {
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return e;
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} else {
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auto f = [=](expr const & m, unsigned) -> expr {
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if (is_metavar(m) && env.contains(m)) {
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expr s = env.get_subst(m);
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return s ? s : m;
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} else {
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return m;
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}
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};
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return replace_fn<decltype(f)>(f)(e);
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}
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}
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meta_ctx add_lift(meta_ctx const & ctx, unsigned s, unsigned n) {
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if (n == 0) {
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return ctx;
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} else if (ctx) {
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meta_entry e = head(ctx);
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// Simplification rule
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// lift:(s1+n1):n2 lift:s1:n1 ---> lift:s1:n1+n2
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if (e.is_lift() && s == e.s() + e.n()) {
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return add_lift(tail(ctx), e.s(), e.n() + n);
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}
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}
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return cons(mk_lift(s, n), ctx);
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}
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expr add_lift(expr const & m, unsigned s, unsigned n) {
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return mk_metavar(metavar_idx(m), add_lift(metavar_ctx(m), s, n));
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}
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meta_ctx add_inst(meta_ctx const & ctx, unsigned s, expr const & v) {
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if (ctx) {
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meta_entry e = head(ctx);
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if (e.is_lift() && e.s() <= s && s < e.s() + e.n()) {
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return add_lift(tail(ctx), e.s(), e.n() - 1);
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}
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// Simplifications such as
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// inst:4 #6 lift:5:3 --> lift:4:2
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// inst:3 #7 lift:4:5 --> lift:3:4
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// General rule is:
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// inst:(s-1) #(s+n-2) lift:s:n --> lift:s-1:n-1
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if (e.is_lift() && is_var(v) && e.s() > 0 && s == e.s() - 1 && e.s() + e.n() > 2 && var_idx(v) == e.s() + e.n() - 2) {
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return add_lift(tail(ctx), e.s() - 1, e.n() - 1);
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}
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}
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return cons(mk_inst(s, v), ctx);
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}
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expr add_inst(expr const & m, unsigned s, expr const & v) {
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return mk_metavar(metavar_idx(m), add_inst(metavar_ctx(m), s, v));
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}
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bool has_meta_context(expr const & m) {
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return metavar_ctx(m);
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}
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expr pop_meta_context(expr const & m) {
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lean_assert(has_meta_context(m));
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return mk_metavar(metavar_idx(m), tail(metavar_ctx(m)));
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}
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struct found_assigned {};
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bool has_assigned_metavar(expr const & e, metavar_env const & menv) {
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if (!has_metavar(e)) {
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return false;
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} else {
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auto proc = [&](expr const & n, unsigned) {
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if (is_metavar(n) && menv.contains(n) && menv.is_assigned(n))
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throw found_assigned();
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};
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for_each_fn<decltype(proc)> visitor(proc);
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try {
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visitor(e);
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return false;
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} catch (found_assigned&) {
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return true;
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}
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}
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}
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/**
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\brief Auxiliary exception used to sign that a metavariable was
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found in an expression.
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*/
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struct found_metavar {};
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bool has_metavar(expr const & e, unsigned midx, metavar_env const & menv) {
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auto f = [&](expr const & m, unsigned) {
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if (is_metavar(m)) {
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unsigned midx2 = metavar_idx(m);
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if (midx2 == midx)
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throw found_metavar();
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if (menv.contains(midx2) &&
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menv.is_assigned(midx2) &&
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has_metavar(menv.get_subst(midx2), midx, menv))
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throw found_metavar();
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}
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};
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try {
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for_each_fn<decltype(f)> proc(f);
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proc(e);
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return false;
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} catch (found_metavar) {
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return true;
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}
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}
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}
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