96 lines
3 KiB
C++
96 lines
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 "util/buffer.h"
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#include "kernel/expr.h"
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#include "kernel/expr_maps.h"
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namespace lean {
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/**
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\brief Default replace_fn postprocessor functional object. It is a
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do-nothing object.
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*/
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class default_replace_postprocessor {
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public:
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void operator()(expr const & old_e, expr const & new_e) {}
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};
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/**
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\brief Functional for applying <tt>F</tt> to the subexpressions of a given expression.
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The signature of \c F is
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expr const &, unsigned -> expr
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F is invoked for each subexpression \c s of the input expression e.
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In a call <tt>F(s, n)</tt>, n is the scope level, i.e., the number of
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bindings operators that enclosing \c s.
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P is a "post-processing" functional object that is applied to each
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pair (old, new)
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*/
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template<typename F, typename P = default_replace_postprocessor>
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class replace_fn {
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static_assert(std::is_same<typename std::result_of<F(expr const &, unsigned)>::type, expr>::value,
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"replace_fn: return type of F is not expr");
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expr_cell_offset_map<expr> m_cache;
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F m_f;
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P m_post;
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expr apply(expr const & e, unsigned offset) {
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bool sh = false;
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if (is_shared(e)) {
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expr_cell_offset p(e.raw(), offset);
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auto it = m_cache.find(p);
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if (it != m_cache.end())
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return it->second;
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sh = true;
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}
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expr r = m_f(e, offset);
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if (is_eqp(e, r)) {
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switch (e.kind()) {
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case expr_kind::Type: case expr_kind::Value: case expr_kind::Constant:
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case expr_kind::Var: case expr_kind::MetaVar:
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break;
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case expr_kind::App:
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r = update_app(e, [=](expr const & c) { return apply(c, offset); });
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break;
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case expr_kind::Eq:
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r = update_eq(e, [=](expr const & l, expr const & r) { return std::make_pair(apply(l, offset), apply(r, 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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r = update_abst(e, [=](expr const & t, expr const & b) { return std::make_pair(apply(t, offset), apply(b, offset+1)); });
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break;
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case expr_kind::Let:
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r = update_let(e, [=](expr const & t, expr const & v, expr const & b) {
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expr new_t = t ? apply(t, offset) : expr();
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return std::make_tuple(new_t, apply(v, offset), apply(b, offset+1));
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});
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break;
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}
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}
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if (sh)
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m_cache.insert(std::make_pair(expr_cell_offset(e.raw(), offset), r));
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m_post(e, r);
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return r;
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}
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public:
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replace_fn(F const & f, P const & p = P()):
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m_f(f),
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m_post(p) {
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}
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expr operator()(expr const & e) {
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return apply(e, 0);
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}
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};
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}
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