lean2/src/kernel/free_vars.cpp

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/*
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 "free_vars.h"
#include "sets.h"
namespace lean {
class has_free_var_functor {
expr_cell_offset_set m_visited;
public:
bool apply(expr const & e, unsigned offset) {
// handle easy cases
switch (e.kind()) {
case expr_kind::Constant: case expr_kind::Prop: case expr_kind::Type: case expr_kind::Numeral:
return false;
case expr_kind::Var:
return var_idx(e) >= offset;
case expr_kind::App: case expr_kind::Lambda: case expr_kind::Pi:
break;
}
if (e.raw()->is_closed())
return false;
if (is_shared(e)) {
expr_cell_offset p(e.raw(), offset);
if (m_visited.find(p) != m_visited.end())
return false;
m_visited.insert(p);
}
bool result = false;
switch (e.kind()) {
case expr_kind::Constant: case expr_kind::Prop: case expr_kind::Type: case expr_kind::Numeral: case expr_kind::Var:
// easy cases were already handled
lean_unreachable(); return false;
case expr_kind::App:
result = std::any_of(begin_args(e), end_args(e), [=](expr const & arg){ return apply(arg, offset); });
break;
case expr_kind::Lambda:
case expr_kind::Pi:
result = apply(abst_type(e), offset) || apply(abst_body(e), offset + 1);
break;
}
if (!result)
e.raw()->set_closed();
return result;
}
};
bool has_free_vars(expr const & e) {
has_free_var_functor f;
return f.apply(e, 0);
}
}