293 lines
8.2 KiB
C++
293 lines
8.2 KiB
C++
/*
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DiffListGeneration(Test) - demonstrate list diff generation
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Copyright (C) Lumiera.org
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2014, 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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#include "lib/test/run.hpp"
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#include "lib/diff/list-diff.hpp"
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#include "lib/iter-adapter.hpp"
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#include "lib/itertools.hpp"
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#include "lib/util.hpp"
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#include <string>
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#include <vector>
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using lib::append_all;
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using util::unConst;
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using util::isnil;
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using std::string;
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using std::vector;
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using std::move;
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using std::swap;
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namespace lib {
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namespace diff{
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//#########################
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template<typename VAL>
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class IndexTable
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{
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public:
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template<class SEQ>
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IndexTable(SEQ const& seq)
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{
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UNIMPLEMENTED("build index");
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}
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size_t
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size() const
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{
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UNIMPLEMENTED("sequence size");
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}
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};
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template<class SEQ>
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class DiffDetector
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{
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using Val = typename SEQ::value_type;
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using Idx = IndexTable<Val>;
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Idx refIdx_;
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SEQ const& currentData_;
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using DiffStep = typename ListDiffLanguage<Val>::DiffStep;
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/** @internal state frame for diff detection and generation. */
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class DiffFrame;
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public:
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explicit
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DiffDetector(SEQ const& refSeq)
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: refIdx_(refSeq)
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, currentData_(refSeq)
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{ }
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/** does the current state of the underlying sequence differ
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* from the state embodied into the last reference snapshot taken?
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* @remarks will possibly evaluate and iterate the whole sequence
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*/
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bool
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isChanged() const
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{
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UNIMPLEMENTED("change detection");
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}
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/** Diff is a iterator to yield a sequence of DiffStep elements */
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using Diff = lib::IterStateWrapper<DiffStep, DiffFrame>;
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/** Diff generation core operation.
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* Take a snapshot of the \em current state of the underlying sequence
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* and establish a frame to find the differences to the previously captured
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* \em old state. This possible difference evaluation is embodied into a #Diff
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* iterator and handed over to the client, while the snapshot of the current state
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* becomes the new reference point from now on.
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* @return iterator to yield a sequence of DiffStep tokens, which describe the changes
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* between the previous reference state and the current state of the sequence.
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* @note takes a new snapshot to supersede the old one, i.e. updates the DiffDetector.
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* @warning the returned iterator retains a reference to the current (new) snapshot.
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* Any concurrent modification leads to undefined behaviour. You must not
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* invoke #pullUpdate while another client still explores the result
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* of an old evaluation.
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*/
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Diff
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pullUpdate()
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{
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Idx mark (currentData_);
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swap (mark, refIdx_); // mark now refers to old reference point
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return Diff(DiffFrame(refIdx_, move(mark)));
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}
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};
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/**
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* A diff generation process is built on top of an "old" reference point
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* and a "new" state of the underlying sequence. Within this reference frame,
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* an demand-driven evaluation of the differences is handed out to the client
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* as an iterator. While consuming this evaluation process, both the old and
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* the new version of the sequence will be traversed once. In case of re-orderings,
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* a nested forward lookup similar to insertion sort will look for matches in the
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* old sequence, rendering the whole evaluation quadratic in worst-case.
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*/
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template<class SEQ>
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class DiffDetector<SEQ>::DiffFrame
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{
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Idx old_;
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Idx* new_;
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size_t oldHead_=0,
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newHead_=0;
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static ListDiffLanguage<Val> token;
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DiffStep currentStep_{token.skip (Val())};
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bool hasOld() const { return oldHead_ < old_.size(); }
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bool hasNew() const { return newHead_ < new_->size(); }
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public:
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DiffFrame(Idx& current, Idx&& refPoint)
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: old_(refPoint)
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, new_(¤t)
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{ }
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/* === Iteration control API for IterStateWrapper== */
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friend bool
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checkPoint (DiffFrame const& frame)
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{
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return frame.hasNew() || frame.hasOld();
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}
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friend DiffStep&
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yield (DiffFrame const& frame)
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{
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REQUIRE (checkPoint (frame));
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return unConst(frame).currentStep_;
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}
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friend void
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iterNext (DiffFrame & frame)
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{
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frame.establishInvariant();
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}
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private:
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void
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establishInvariant()
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{
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if (canPick())
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{
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}
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}
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bool
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canPick()
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{
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return false;//TODO
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}
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};
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/** allocate static storage for the diff language token builder functions */
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template<class SEQ>
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ListDiffLanguage<typename DiffDetector<SEQ>::Val> DiffDetector<SEQ>::DiffFrame::token;
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//#########################
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namespace test{
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namespace {//Test fixture....
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using DataSeq = vector<string>;
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#define TOK(id) id(STRINGIFY(id))
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string TOK(a1), TOK(a2), TOK(a3), TOK(a4), TOK(a5);
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string TOK(b1), TOK(b2), TOK(b3), TOK(b4);
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using Interpreter = ListDiffInterpreter<string>;
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using DiffStep = ListDiffLanguage<string>::DiffStep;
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using DiffSeq = vector<DiffStep>;
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DiffStep_CTOR(ins);
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DiffStep_CTOR(del);
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DiffStep_CTOR(pick);
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DiffStep_CTOR(find);
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DiffStep_CTOR(skip);
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}//(End)Test fixture
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/***********************************************************************//**
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* @test Demonstration/Concept: how to derive a list diff representation
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* from the comparison of two sequences. The changes necessary to
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* transform one sequence into the other one are given as a linear
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* sequence of elementary mutation operations.
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*
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* The change detector assumes elements with well defined identity
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* and uses an index table for both sequences. The diff is generated
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* progressively, demand-driven.
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*
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* @see DiffListApplication_test
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*/
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class DiffListGeneration_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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DataSeq toObserve({a1,a2,a3,a4,a5});
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DiffDetector<DataSeq> detector(toObserve);
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CHECK (!detector.isChanged());
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toObserve = {b1,a3,a5,b2,b3,a4,b4};
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CHECK (detector.isChanged());
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auto changes = detector.pullUpdate();
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CHECK (!isnil (changes));
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CHECK (!detector.isChanged());
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DiffSeq generatedDiff;
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append_all (changes, generatedDiff);
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CHECK (generatedDiff == DiffSeq({del(a1)
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, del(a2)
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, ins(b1)
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, pick(a3)
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, find(a5)
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, ins(b2)
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, ins(b3)
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, pick(a4)
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, skip(a5)
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, ins(b4)
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}));
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}
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};
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/** Register this test class... */
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LAUNCHER (DiffListGeneration_test, "unit common");
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}}} // namespace lib::diff::test
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