128 lines
3.7 KiB
C++
128 lines
3.7 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 <algorithm>
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#include "free_vars.h"
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#include "sets.h"
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#include "replace.h"
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namespace lean {
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/** \brief Functional object for checking whether a kernel expression has free variables or not. */
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class has_free_vars_fn {
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protected:
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expr_cell_offset_set m_visited;
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virtual bool process_var(expr const & x, unsigned offset) {
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return var_idx(x) >= offset;
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}
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bool apply(expr const & e, unsigned offset) {
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// handle easy cases
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switch (e.kind()) {
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case expr_kind::Constant: case expr_kind::Type: case expr_kind::Value:
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return false;
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case expr_kind::Var:
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return process_var(e, offset);
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case expr_kind::App: case expr_kind::Eq: case expr_kind::Lambda: case expr_kind::Pi: case expr_kind::Let:
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break;
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}
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if (e.raw()->is_closed())
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return false;
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if (is_shared(e)) {
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expr_cell_offset p(e.raw(), offset);
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if (m_visited.find(p) != m_visited.end())
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return false;
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m_visited.insert(p);
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}
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bool result = false;
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switch (e.kind()) {
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case expr_kind::Constant: case expr_kind::Type: case expr_kind::Value: case expr_kind::Var:
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// easy cases were already handled
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lean_unreachable(); return false;
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case expr_kind::App:
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result = std::any_of(begin_args(e), end_args(e), [=](expr const & arg){ return apply(arg, offset); });
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break;
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case expr_kind::Eq:
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result = apply(eq_lhs(e), offset) || apply(eq_rhs(e), offset);
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break;
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case expr_kind::Lambda:
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case expr_kind::Pi:
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result = apply(abst_domain(e), offset) || apply(abst_body(e), offset + 1);
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break;
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case expr_kind::Let:
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result = apply(let_value(e), offset) || apply(let_body(e), offset + 1);
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break;
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}
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if (!result)
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e.raw()->set_closed();
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return result;
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}
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public:
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bool operator()(expr const & e) { return apply(e, 0); }
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};
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bool has_free_vars(expr const & e) {
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return has_free_vars_fn()(e);
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}
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/** \brief Functional object for checking whether a kernel expression has a free variable in the range <tt>[low, high)</tt> or not. */
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class has_free_var_in_range_fn : public has_free_vars_fn {
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unsigned m_low;
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unsigned m_high;
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virtual bool process_var(expr const & x, unsigned offset) {
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return var_idx(x) >= offset + m_low && var_idx(x) < offset + m_high;
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}
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public:
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has_free_var_in_range_fn(unsigned low, unsigned high):m_low(low), m_high(high) {
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lean_assert(low < high);
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}
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};
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bool has_free_var(expr const & e, unsigned vidx) {
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return has_free_var_in_range_fn(vidx, vidx+1)(e);
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}
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bool has_free_var(expr const & e, unsigned low, unsigned high) {
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return has_free_var_in_range_fn(low, high)(e);
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}
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expr lower_free_vars(expr const & e, unsigned d) {
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lean_assert(d > 0);
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lean_assert(!has_free_var(e, 0, d));
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auto f = [=](expr const & e, unsigned offset) -> expr {
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if (is_var(e) && var_idx(e) >= offset) {
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lean_assert(var_idx(e) >= offset + d);
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return var(var_idx(e) - d);
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}
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else {
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return e;
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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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expr lift_free_vars(expr const & e, unsigned d) {
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if (d == 0)
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return e;
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auto f = [=](expr const & e, unsigned offset) -> expr {
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if (is_var(e) && var_idx(e) >= offset) {
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return var(var_idx(e) + d);
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}
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else {
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return e;
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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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