75 lines
2.8 KiB
C++
75 lines
2.8 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 <limits>
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#include "kernel/free_vars.h"
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#include "kernel/expr_sets.h"
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#include "kernel/replace_fn.h"
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#include "kernel/for_each_fn.h"
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namespace lean {
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bool has_free_var(expr const & e, unsigned i) {
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bool found = false;
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for_each(e, [&](expr const & e, unsigned offset) {
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if (found)
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return false; // already found
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unsigned n_i = i + offset;
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if (n_i < i)
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return false; // overflow, vidx can't be >= max unsigned
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if (n_i >= get_free_var_range(e))
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return false; // expression e does not contain free variables with idx >= n_i
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if (is_var(e)) {
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unsigned vidx = var_idx(e);
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if (vidx == n_i)
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found = true;
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}
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return true; // continue search
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});
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return found;
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}
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expr lower_free_vars(expr const & e, unsigned s, unsigned d) {
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if (d == 0 || s >= get_free_var_range(e))
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return e;
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lean_assert(s >= d);
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return replace(e, [=](expr const & e, unsigned offset) -> optional<expr> {
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unsigned s1 = s + offset;
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if (s1 < s)
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return some_expr(e); // overflow, vidx can't be >= max unsigned
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if (s1 >= get_free_var_range(e))
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return some_expr(e); // expression e does not contain free variables with idx >= s1
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if (is_var(e) && var_idx(e) >= s1) {
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lean_assert(var_idx(e) >= offset + d);
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return some_expr(mk_var(var_idx(e) - d));
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} else {
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return none_expr();
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}
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});
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}
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expr lower_free_vars(expr const & e, unsigned d) { return lower_free_vars(e, d, d); }
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expr lift_free_vars(expr const & e, unsigned s, unsigned d) {
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if (d == 0 || s >= get_free_var_range(e))
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return e;
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return replace(e, [=](expr const & e, unsigned offset) -> optional<expr> {
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unsigned s1 = s + offset;
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if (s1 < s)
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return some_expr(e); // overflow, vidx can't be >= max unsigned
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if (s1 >= get_free_var_range(e))
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return some_expr(e); // expression e does not contain free variables with idx >= s1
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if (is_var(e) && var_idx(e) >= s + offset) {
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unsigned new_idx = var_idx(e) + d;
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if (new_idx < var_idx(e))
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throw exception("invalid lift_free_vars operation, index overflow");
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return some_expr(mk_var(new_idx));
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} else {
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return none_expr();
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}
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});
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}
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expr lift_free_vars(expr const & e, unsigned d) { return lift_free_vars(e, 0, d); }
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}
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