on closer investigation it turned out that the logic of the first design attempt was broken altogether. It did not properly support backtracking (which was the reason to start this whole exercise) and it caused dangling references within the lambda closure once the produced iterator pipeline was moved out into the target location. Reasoning from first principles then indicated that the only sane way to build such a search evaluation component is to use *two* closely collaborating layers. The actual filter configuration and evaluation logic can not reside and work from within the expander. Rather, it must sit in a layer on top and work in a conventional, imperative way (with a while loop). Sometimes, functional programming is *not* the natural way of doing things, and we should then stop attempting to force matters against their nature.
188 lines
5.9 KiB
C++
188 lines
5.9 KiB
C++
/*
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IterChainSearch(Test) - verify chained search operations with backtracking
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Copyright (C) Lumiera.org
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2018, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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* *****************************************************/
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/** @file iter-chain-search-test.cpp
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** unit test \ref IterChainSearch_test
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*/
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#include "lib/test/run.hpp"
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#include "lib/test/test-helper.hpp"
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#include "lib/format-util.hpp" /////////////////////////////TODO necessary?
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#include "lib/format-cout.hpp" /////////////////////////////TODO necessary?
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#include "lib/iter-chain-search.hpp"
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#include "lib/util.hpp"
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#include <vector>
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#include <string>
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namespace lib {
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namespace iter{
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namespace test{
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using ::Test;
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using util::join;
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using util::isnil;
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using util::startsWith;
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using util::isSameObject;
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using std::vector;
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using std::string;
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using lumiera::error::LERR_(ITER_EXHAUST);
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namespace { // test fixture
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using Spam = vector<string>;
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const Spam SPAM{"spam"
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,"sausage"
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,"spam"
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,"spam"
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,"bacon"
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,"spam"
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,"tomato"
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,"and"
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,"spam"
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};
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} // (END)fixture
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///////////////////////////////////////////////////TODO WIP
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#define SHOW_TYPE(_TY_) \
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cout << "typeof( " << STRINGIFY(_TY_) << " )= " << lib::meta::typeStr<_TY_>() <<endl;
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#define SHOW_EXPR(_XX_) \
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cout << "Probe " << STRINGIFY(_XX_) << " ? = " << _XX_ <<endl;
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/** Diagnostic helper: join all the elements from a _copy_ of the iterator */
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template<class II>
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inline string
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materialise (II&& ii)
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{
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return util::join (std::forward<II> (ii), "-");
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}
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///////////////////////////////////////////////////TODO WIP
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/*****************************************************************//**
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* @test verify a setup for consecutive searches with backtracking.
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*
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* @see iter-chain-search.hpp
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* @see iter-cursor.hpp
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* @see [usage example](event-log.hpp)
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*/
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class IterChainSearch_test : public Test
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{
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virtual void
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run (Arg)
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{
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simpleSearch();
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chainedIteration();
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backtracking();
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}
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/** @test simple basic use case. */
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void
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simpleSearch ()
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{
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auto search = chainSearch(SPAM)
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.search("bacon")
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.search("tomato");
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CHECK (search);
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CHECK (not isnil(search));
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CHECK ("tomato" == *search);
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CHECK (isSameObject (*search, SPAM[6]));
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search.clearFilter();
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CHECK ("tomato" == *search);
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++search;
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CHECK ("and" == *search);
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search.search("spam");
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CHECK ("spam" == *search);
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CHECK (isSameObject (*search, SPAM[8]));
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++search;
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CHECK (not search);
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CHECK (isnil (search));
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VERIFY_ERROR (ITER_EXHAUST, *search);
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}
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/** @test verify consecutive application of several functors on the underlying filter.
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* In the general case, each step in the chain is a function working on a copy of the
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* current filter state. Since each such step configures its own copy of the complete
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* pipeline, it may reconfigure this filter pipeline in arbitrary ways. After exhausting
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* the last layer, the evaluation returns to the previous layer, but immediately re-applies
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* the configuration step on the then next element.
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*/
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void
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chainedIteration ()
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{
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auto search = chainSearch(SPAM)
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.search([](string const& str){ return startsWith (str, "s"); });
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///////////////////////////////////////////////////TODO WIP
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cout << materialise (search) <<endl;
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///////////////////////////////////////////////////TODO WIP
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CHECK (search);
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search.addStep([](auto filter)
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{
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string currVal = *filter;
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filter.setNewFilter ([=](string const& val){
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return val != currVal; });
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});
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///////////////////////////////////////////////////TODO WIP
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cout << materialise (search) <<endl;
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///////////////////////////////////////////////////TODO WIP
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}
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/** @test verify a complex search with backtracking.
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* This becomes relevant when a given search condition can be "too greedy" for the
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* complete chain to succeed. Most notably this is the case when the search is fundamentally
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* reconfigured in some steps, e.g. by switching the search orientation. To demonstrate this,
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* we use a "gear switching" iterator, which allows us to reverse the direction and to search
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* backwards from the current position. We configure the second condition in the chain such
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* that it can not succeed when starting from the first match on the first condition
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*/
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void
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backtracking ()
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{
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}
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};
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LAUNCHER (IterChainSearch_test, "unit common");
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}}} // namespace lib::iter::test
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