80 lines
3.3 KiB
C++
80 lines
3.3 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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#pragma once
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#include "kernel/expr.h"
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#include "kernel/expr_sets.h"
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namespace lean {
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/** \brief Identity function for expressions. */
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struct id_expr_fn {
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expr const & operator()(expr const & e) const { return e; }
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};
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/**
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\brief Functional object for comparing expressions.
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The parameter N is a normalization function that can be used
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to normalize sub-expressions before comparing them.
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The hashcode of expressions is used to optimize the comparison when
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parameter UseHash == true. We should set UseHash to false when N
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is not the identity function.
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*/
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template<typename N = id_expr_fn, bool UseHash = true>
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class expr_eq_fn {
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expr_cell_pair_set m_eq_visited;
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N m_norm;
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bool apply(expr const & a0, expr const & b0) {
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if (is_eqp(a0, b0)) return true;
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if (!a0 || !b0) return false;
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if (UseHash && a0.hash() != b0.hash()) return false;
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expr const & a = m_norm(a0);
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expr const & b = m_norm(b0);
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if (a.kind() != b.kind()) return false;
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if (is_var(a)) return var_idx(a) == var_idx(b);
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if (is_shared(a) && is_shared(b)) {
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auto p = std::make_pair(a.raw(), b.raw());
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if (m_eq_visited.find(p) != m_eq_visited.end())
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return true;
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m_eq_visited.insert(p);
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}
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switch (a.kind()) {
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case expr_kind::Var: lean_unreachable();
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case expr_kind::Constant: return const_name(a) == const_name(b);
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case expr_kind::App:
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if (num_args(a) != num_args(b))
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return false;
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for (unsigned i = 0; i < num_args(a); i++)
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if (!apply(arg(a, i), arg(b, i)))
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return false;
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return true;
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case expr_kind::Eq: return apply(eq_lhs(a), eq_lhs(b)) && apply(eq_rhs(a), eq_rhs(b));
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case expr_kind::Lambda: // Remark: we ignore get_abs_name because we want alpha-equivalence
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case expr_kind::Pi: return apply(abst_domain(a), abst_domain(b)) && apply(abst_body(a), abst_body(b));
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case expr_kind::Type: return ty_level(a) == ty_level(b);
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case expr_kind::Value: return to_value(a) == to_value(b);
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case expr_kind::Let: return apply(let_type(a), let_type(b)) && apply(let_value(a), let_value(b)) && apply(let_body(a), let_body(b));
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case expr_kind::MetaVar:
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return metavar_idx(a) == metavar_idx(b) &&
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compare(metavar_ctx(a), metavar_ctx(b), [&](meta_entry const & e1, meta_entry const & e2) {
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if (e1.kind() != e2.kind() || e1.s() != e2.s())
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return false;
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if (e1.is_inst())
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return apply(e1.v(), e2.v());
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else
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return e1.n() == e2.n();
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});
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}
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lean_unreachable();
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}
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public:
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expr_eq_fn(N const & norm = N()):m_norm(norm) {}
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bool operator()(expr const & a, expr const & b) {
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return apply(a, b);
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}
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void clear() { m_eq_visited.clear(); }
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};
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}
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