85e3f51fd5
foldr combinator is used to define brec_on recursor. It is easier to access the brec_on "dictionary" if the representation is uniform.
53 lines
1.9 KiB
C++
53 lines
1.9 KiB
C++
/*
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Copyright (c) 2014 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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namespace lean {
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/** \brief Return true iff \c t is of the form <tt>((f s1) s2)</tt> */
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bool is_bin_app(expr const & t, expr const & f);
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/** \brief Return true iff \c t is of the form <tt>((f s1) s2)</tt>, if the result is true, then store a1 -> lhs, a2 -> rhs */
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bool is_bin_app(expr const & t, expr const & f, expr & lhs, expr & rhs);
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/** \brief Return unit if <tt>num_args == 0</tt>, args[0] if <tt>num_args == 1</tt>, and
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<tt>(op args[0] (op args[1] (op ... )))</tt> */
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expr mk_bin_rop(expr const & op, expr const & unit, unsigned num_args, expr const * args);
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expr mk_bin_rop(expr const & op, expr const & unit, std::initializer_list<expr> const & l);
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/** \brief Version of foldr that only uses unit when num_args == 0 */
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template<typename MkBin, typename MkUnit>
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expr foldr_compact(MkBin && mkb, MkUnit && mku, unsigned num_args, expr const * args) {
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if (num_args == 0) {
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return mku();
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} else {
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expr r = args[num_args - 1];
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unsigned i = num_args - 1;
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while (i > 0) {
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--i;
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r = mkb(args[i], r);
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}
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return r;
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}
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}
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/** \brief Version of foldr that only uses unit when num_args == 0 */
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template<typename MkBin, typename MkUnit>
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expr foldr(MkBin && mkb, MkUnit && mku, unsigned num_args, expr const * args) {
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expr r = mku();
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unsigned i = num_args;
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while (i > 0) {
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--i;
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r = mkb(args[i], r);
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}
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return r;
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}
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/** \brief Return unit if <tt>num_args == 0</tt>, args[0] if <tt>num_args == 1</tt>, and
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<tt>(op ... (op (op args[0] args[1]) args[2]) ...)</tt> */
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expr mk_bin_lop(expr const & op, expr const & unit, unsigned num_args, expr const * args);
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expr mk_bin_lop(expr const & op, expr const & unit, std::initializer_list<expr> const & l);
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}
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