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Library: build a helper to encapsulate container access by index

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...mostly we want the usual convenient handling pattern for iterators,
but with the proviso actually to perform an access by subscript,
and the ability to re-set to another current index
This commit is contained in:
Fischlurch 2024-03-20 23:58:42 +01:00
parent 76bd9ba6ce
commit f716fb0bee
3 changed files with 506 additions and 15 deletions
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144
src/lib/iter-index.hpp Normal file
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@ -0,0 +1,144 @@
/*
ITER-INDEX.hpp - iterator with indexed random-access to referred container
Copyright (C) Lumiera.org
2024, Hermann Vosseler <Ichthyostega@web.de>
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of
the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/** @file iter-index.hpp
** Iterator-style access handle to a referred container with subscript index.
** This wrapper packages a current index number and a back-link to some data container
** with subscript operator and range check. This allows to hand out a navigable access point
** to a processing algorithm while abstracting away the actual data storage. Besides usage
** as »Lumiera Forward Iterator«, the current access position can be retrieved directly
** and it can be relocated to another valid index position; this implies also the ability
** to re-set the iteration to the container's start.
**
** @see IterIndex_test
** @see iter-adapter.hpp
** @see [usage example](\ref lib::TextTemplate::InstanceCore)
**
*/
#ifndef SRC_LIB_ITER_INDEX_H
#define SRC_LIB_ITER_INDEX_H
#include "lib/iter-adapter.hpp"
//#include <type_traits>
//#include <utility>
namespace lib {
namespace {// Implementation of the access core
template<typename PTR>
struct IndexAccessCore
{
PTR data_{};
size_t idx_{0};
using ResVal = decltype(data_->operator[](0));
using value_type = typename meta::RefTraits<ResVal>::Value;
using reference = typename meta::RefTraits<ResVal>::Reference;
using IterWrapper = lib::IterStateWrapper<value_type, IndexAccessCore>;
bool
checkPoint() const
{
return isValidIDX(idx_);
}
reference
yield() const
{
return (*data_)[idx_];
}
void
iterNext()
{
++idx_;
}
bool
isValidIDX (size_t idx) const
{
return bool(data_)
and idx < data_->size();
}
friend bool operator== (IndexAccessCore const& c1, IndexAccessCore const& c2)
{
return c1.data_ == c2.data_ and (not c1.data_ or c1.idx_ == c2.idx_);
}
friend bool operator!= (IndexAccessCore const& c1, IndexAccessCore const& c2)
{
return not (c1 == c2);
}
};
}//(End)Implementation
/**
*
*/
template<class CON, typename PTR = CON*>
class IterIndex
: public IndexAccessCore<PTR>::IterWrapper
{
using _Cor = IndexAccessCore<PTR>;
using _Par = typename _Cor::IterWrapper;
public:
IterIndex() = default;
IterIndex (CON& dataContainer)
: _Par{_Cor{&dataContainer, 0}}
{ }
size_t
getIDX() const
{
_Par::__throw_if_empty();
return const_cast<IterIndex*>(this)->stateCore().idx_;
}
void
setIDX (size_t newIDX)
{
auto& core = _Par::stateCore();
if (not core.isValidIDX (newIDX))
throw lumiera::error::Invalid ("Attempt to set index out of bounds",
lumiera::error::LUMIERA_ERROR_INDEX_BOUNDS);
core.idx_ = newIDX;
}
};
} // namespace lib
#endif /*SRC_LIB_ITER_INDEX_H*/

265
tests/library/iter-index-test.cpp Normal file
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@ -0,0 +1,265 @@
/*
IterIndex(Test) - verify index access packaged as iterator handle
Copyright (C) Lumiera.org
2024, Hermann Vosseler <Ichthyostega@web.de>
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of
the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
* *****************************************************/
/** @file iter-index-test.cpp
** unit test \ref IterIndex_test
*/
#include "lib/test/run.hpp"
#include "lib/iter-index.hpp"
#include "lib/test/test-helper.hpp"
#include "lib/iter-explorer.hpp"
#include "lib/format-util.hpp"
#include "lib/util.hpp"
#include <vector>
namespace lib {
namespace test{
using ::Test;
using util::join;
using util::isnil;
using std::vector;
using LERR_(ITER_EXHAUST);
using LERR_(INDEX_BOUNDS);
namespace { // test fixture
const uint NUM_ELMS = 10;
using Numz = vector<uint>;
using Iter = IterIndex<Numz>;
using CIter = IterIndex<const Numz>;
inline Numz
makeNumz()
{
Numz numz;
for (uint i=0; i<NUM_ELMS; ++i)
numz.push_back(i);
return numz;
}
} // (END)fixture
/*****************************************************************//**
* @test demonstrate and cover the properties of IterCursor.
* This wrapper allows to change between iterating forward and backwards.
*
* @see iter-cursor.hpp
* @see iter-adapter.hpp
* @see [usage example](\ref event-log.hpp)
*/
class IterIndex_test : public Test
{
virtual void
run (Arg)
{
simpleIteration();
verify_randomAccess();
iterTypeVariations();
}
/** @test just iterate in various ways. */
void
simpleIteration ()
{
Numz numz{makeNumz()};
Iter i1{numz};
CHECK (not isnil(i1));
CHECK (0 == *i1);
++++++i1;
CHECK (3 == *i1);
for (uint i=*i1 ; i1; ++i1, ++i)
CHECK (i == *i1);
CHECK (isnil(i1));
auto sum = explore(Iter{numz}).resultSum();
uint n = numz.size() - 1;
CHECK (sum == n*(n+1)/2);
for (auto & i : Iter{numz})
++i; // note: manipulate the contents...
CHECK (join(numz,"◇") == "1◇2◇3◇4◇5◇6◇7◇8◇9◇10"_expect);
verifyComparisons (Iter{numz});
}
/** @test verify the ability of IterCursor to switch
* the direction of the iteration. This "gear switch" can be done
* any time, while in the middle of iteration, and even after
* iteration end. That means, even an exhausted iterator can be
* "turned back". This does not work on a default constructed
* IterCursor, though.
*/
void
verify_randomAccess ()
{
Numz numz{makeNumz()};
Iter iter{numz};
CHECK (0 == *iter);
++++++++iter;
CHECK (4 == *iter);
CHECK (not isnil(iter));
CHECK (join(iter) == "4, 5, 6, 7, 8, 9"_expect);
verifyComparisons (iter);
CHECK (4 == *iter);
CHECK (4 == iter.getIDX());
iter.setIDX(7);
CHECK (7 == iter.getIDX());
CHECK (not isnil(iter));
CHECK (7 == *iter);
++iter;
CHECK (8 == *iter);
iter.setIDX(6);
CHECK (join(iter) == "6, 7, 8, 9"_expect);
verifyComparisons (iter);
++++++++iter;
CHECK (isnil(iter));
VERIFY_ERROR (ITER_EXHAUST, *iter);
VERIFY_ERROR (ITER_EXHAUST, ++iter);
VERIFY_ERROR (ITER_EXHAUST, iter.getIDX());
iter.setIDX(9);
CHECK (not isnil(iter));
CHECK (9 == *iter);
VERIFY_ERROR (INDEX_BOUNDS, iter.setIDX(10));
CHECK (9 == iter.getIDX());
VERIFY_ERROR (INDEX_BOUNDS, iter.setIDX(-1));
CHECK (9 == iter.getIDX());
}
/** @test verify the const and dereferencing variants,
* based on the const-ness of the underlying STL iterator
*/
void
iterTypeVariations ()
{
Numz numz{makeNumz()};
Numz const& const_numz{numz};
uint i = 0;
for (Iter iter{numz};
iter; ++iter, ++i
)
{
CHECK (iter);
CHECK (iter != Iter());
CHECK (*iter == i);
--(*iter);
CHECK (*iter == i-1);
}
i = 0;
for (CIter iter{const_numz};
iter; ++iter, ++i
)
{
CHECK (iter);
CHECK (iter != CIter());
CHECK (*iter == i-1);
// note: the previous run indeed modified
// the elements within the container.
// ++(*iter); // doesn't compile, because it yields a "* const"
}
verifyComparisons (CIter{numz});
}
/** @test verify equality handling and NIL detection
* for the given iterator/wrapper handed in.
* @note the argument is not altered; rather we create
* several copies, to iterate and compare those
*/
template<class IT>
void
verifyComparisons (IT const& ii)
{
IT i1(ii);
IT i2(ii);
IT iN;
CHECK ( isnil (iN));
CHECK (!isnil (i1));
CHECK (!isnil (i2));
CHECK (i1 == i2); CHECK (i2 == i1);
CHECK (i1 != iN); CHECK (iN != i1);
CHECK (i2 != iN); CHECK (iN != i2);
++i1;
CHECK (i1 != i2);
CHECK (i1 != iN);
++i2;
CHECK (i1 == i2);
CHECK (i1 != iN);
CHECK (i2 != iN);
while (++i1) { }
CHECK (isnil(i1));
CHECK (i1 != i2);
CHECK (i1 == iN);
while (++i2) { }
CHECK (isnil(i2));
CHECK (i2 == i1);
CHECK (i2 == iN);
}
};
LAUNCHER (IterIndex_test, "unit common");
}} // namespace lib::test

112
wiki/thinkPad.ichthyo.mm
View file

@ -112553,16 +112553,13 @@ std::cout &lt;&lt; tmpl.render({&quot;what&quot;, &quot;World&quot;}) &lt;&lt; s
<node CREATED="1710888899301" ID="ID_1431488282" MODIFIED="1710889348598" TEXT="mu&#xdf; zuweisbar sein (also letztlich ein Pointer auf die Daten)"/>
<node CREATED="1710889358377" ID="ID_903149258" MODIFIED="1710889479699" TEXT="wird rekursiv / re-entrant verwendet">
<richcontent TYPE="NOTE"><html>
<head>
</head>
<head/>
<body>
<p>
das bedeutet: nachdem ein nested-context <i>ge&#246;ffnet wurde, </i>m&#252;ssen wir einen State erlangen, auf dem transparent genauso gearbeitet werden kann, wie auf dem initialen / top-level-State
</p>
</body>
</html>
</richcontent>
</html></richcontent>
<icon BUILTIN="messagebox_warning"/>
</node>
</node>
@ -112577,16 +112574,13 @@ std::cout &lt;&lt; tmpl.render({&quot;what&quot;, &quot;World&quot;}) &lt;&lt; s
<node CREATED="1710888800147" ID="ID_415681901" MODIFIED="1710888817940" TEXT="konzeptionell wie eine Dreferentiation"/>
<node CREATED="1710888818840" ID="ID_480044105" MODIFIED="1710888865476" TEXT="aber die Implementierung obliegt der DataSrc">
<richcontent TYPE="NOTE"><html>
<head>
</head>
<head/>
<body>
<p>
weil sie im Einzelfall auch komplexer sein kann, und im Besonderen eine parent-Verkn&#252;pfung beinhaltet
</p>
</body>
</html>
</richcontent>
</html></richcontent>
</node>
</node>
</node>
@ -112846,6 +112840,7 @@ std::cout &lt;&lt; tmpl.render({&quot;what&quot;, &quot;World&quot;}) &lt;&lt; s
<node CREATED="1710802648966" ID="ID_307257971" MODIFIED="1710802653691" TEXT="sequence-extractor"/>
</node>
<node CREATED="1710802684313" ID="ID_1755236197" MODIFIED="1710802692132" TEXT="currInstruction">
<arrowlink COLOR="#b43057" DESTINATION="ID_647695428" ENDARROW="Default" ENDINCLINATION="-527;-17;" ID="Arrow_ID_660745747" STARTARROW="None" STARTINCLINATION="211;249;"/>
<node CREATED="1710802696248" ID="ID_1500495122" MODIFIED="1710802702482" TEXT="der instruction pointer"/>
<node CREATED="1710802707078" ID="ID_1676117590" MODIFIED="1710802716696" TEXT="ist zuweisbar (random-access)"/>
</node>
@ -112867,16 +112862,13 @@ std::cout &lt;&lt; tmpl.render({&quot;what&quot;, &quot;World&quot;}) &lt;&lt; s
<node CREATED="1710889546263" ID="ID_1579638728" MODIFIED="1710889557098" TEXT="einschlie&#xdf;lich der M&#xf6;glichkeit verschachtelter States"/>
<node CREATED="1710889557878" ID="ID_1797783109" MODIFIED="1710889645948" TEXT="letzteres ist aber als seltene/optionale Erweiterung anzusetzen">
<richcontent TYPE="NOTE"><html>
<head>
</head>
<head/>
<body>
<p>
will sagen, der Standardfall ist, lediglich auf eine Map per Key zuzugreifen &#8212; und die gesamte Datenstruktur ist hierauf zu optimieren
</p>
</body>
</html>
</richcontent>
</html></richcontent>
</node>
<node CREATED="1710859059558" ID="ID_878052078" MODIFIED="1710889700823" TEXT="eingebettete DataSrc &#x2261; das ist das konkrete Binding">
<node CREATED="1710859078771" ID="ID_283747990" MODIFIED="1710889722804" TEXT="ist zuweisbar (f&#xfc;r nesting)"/>
@ -112908,6 +112900,13 @@ std::cout &lt;&lt; tmpl.render({&quot;what&quot;, &quot;World&quot;}) &lt;&lt; s
</node>
<node BACKGROUND_COLOR="#f0d5c5" COLOR="#990033" CREATED="1710898830750" ID="ID_629945091" MODIFIED="1710898839421" TEXT="ist das auch praktisch machbar?">
<icon BUILTIN="help"/>
<node CREATED="1710977238360" ID="ID_1614727391" MODIFIED="1710977265505" TEXT="sehr wohl &#x2014; genau daf&#xfc;r wurde std::string_view eingef&#xfc;hrt">
<icon BUILTIN="idea"/>
</node>
<node BACKGROUND_COLOR="#e0ceaa" COLOR="#690f14" CREATED="1710977296336" ID="ID_359874280" MODIFIED="1710986480717" TEXT="Vorsicht: string-view ist inh&#xe4;rent gef&#xe4;hrlich">
<arrowlink COLOR="#7b415c" DESTINATION="ID_860112408" ENDARROW="Default" ENDINCLINATION="-3082;815;" ID="Arrow_ID_1628394674" STARTARROW="None" STARTINCLINATION="-1036;64;"/>
<icon BUILTIN="messagebox_warning"/>
</node>
</node>
</node>
<node CREATED="1710901352781" ID="ID_98335183" MODIFIED="1710901434035" TEXT="mu&#xdf; es schon deshalb machen, weil das Rendern einmalig bei der Iteration passiert">
@ -112940,6 +112939,64 @@ std::cout &lt;&lt; tmpl.render({&quot;what&quot;, &quot;World&quot;}) &lt;&lt; s
</node>
</node>
</node>
<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1710978786840" ID="ID_647695428" MODIFIED="1710978844422" TEXT="brauche einen &#xbb;Cursor&#xab; f&#xfc;r aktuelle Action">
<linktarget COLOR="#b43057" DESTINATION="ID_647695428" ENDARROW="Default" ENDINCLINATION="-527;-17;" ID="Arrow_ID_660745747" SOURCE="ID_1755236197" STARTARROW="None" STARTINCLINATION="211;249;"/>
<icon BUILTIN="flag-yellow"/>
<node BACKGROUND_COLOR="#f0d5c5" COLOR="#990033" CREATED="1710978847288" ID="ID_1081341248" MODIFIED="1710978855055" TEXT="hatte ich sowas nicht schon mal?">
<icon BUILTIN="help"/>
<node CREATED="1710979039184" ID="ID_1895789363" LINK="#ID_1801538785" MODIFIED="1710979356636" TEXT="CursorGear">
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<icon BUILTIN="button_cancel"/>
<node CREATED="1710979082768" ID="ID_369083585" MODIFIED="1710979103721" TEXT="IterCursor_test"/>
<node CREATED="1710979301630" ID="ID_46182414" MODIFIED="1710979328828" TEXT="der hei&#xdf;t zwar &#xbb;cursor&#xab; &#x2014; ist aber nur ein vorw&#xe4;rts/r&#xfc;ckw&#xe4;rts-Iterator"/>
<node CREATED="1710979329631" ID="ID_114803277" MODIFIED="1710979349848" TEXT="bildet die Basis f&#xfc;r Suchoperationen auf dem EventLog"/>
</node>
<node CREATED="1710979380360" ID="ID_614355480" MODIFIED="1710979390858" TEXT="kann mich sonst nicht an sowas erinnern"/>
<node CREATED="1710979395354" ID="ID_1076235199" MODIFIED="1710979402633" TEXT="widerspricht auch dem Iterator-Ansatz"/>
</node>
<node BACKGROUND_COLOR="#e0ceaa" COLOR="#690f14" CREATED="1710979423805" ID="ID_1010060877" MODIFIED="1710979484395" TEXT="Iterator gen&#xfc;gt nicht &#x2014; brauche back-Link auf den Basis-Container">
<icon BUILTIN="messagebox_warning"/>
</node>
<node CREATED="1710979486244" ID="ID_443568794" MODIFIED="1710979497911" TEXT="was ich hier brauche ist einfach &#x2014; und generisch">
<icon BUILTIN="idea"/>
</node>
<node COLOR="#338800" CREATED="1710979647405" ID="ID_635270252" MODIFIED="1710986040853" TEXT="IterIndex&lt;CON&gt;">
<icon BUILTIN="button_ok"/>
<node COLOR="#338800" CREATED="1710980823626" ID="ID_1159027894" MODIFIED="1710986027221" TEXT="Struktur: ein State-Wrapper">
<icon BUILTIN="button_ok"/>
<node CREATED="1710980870121" ID="ID_1036626151" MODIFIED="1710980881428" TEXT="Gr&#xf6;&#xdf;e : 2 &#xbb;Slot&#xab;"/>
<node CREATED="1710980885639" ID="ID_1978510735" MODIFIED="1710980895665" TEXT="bettet die Index-Nummer direkt ein"/>
<node CREATED="1710980896470" ID="ID_1734087052" MODIFIED="1710980917374" TEXT="Pointer-Typ konfigurierbar machen (falls Ownership gew&#xfc;nscht)"/>
</node>
<node COLOR="#338800" CREATED="1710981200357" ID="ID_596111172" MODIFIED="1710986024544" TEXT="brauche separate Core als Hilfsklasse">
<icon BUILTIN="button_ok"/>
<node CREATED="1710981216498" ID="ID_1250106024" MODIFIED="1710981224270" TEXT="auch wegen der Typ-Inferenz"/>
<node CREATED="1710983273680" ID="ID_1670736861" MODIFIED="1710983309559" TEXT="einmal kreuzweise typedefs + decltype()"/>
<node BACKGROUND_COLOR="#c8c0b6" CREATED="1710983310267" ID="ID_268611095" MODIFIED="1710983344686">
<richcontent TYPE="NODE"><html>
<head/>
<body>
<p>
uuund fertig &#8212; <b>C++ ist toll</b>
</p>
</body>
</html></richcontent>
<icon BUILTIN="ksmiletris"/>
</node>
</node>
<node BACKGROUND_COLOR="#eef0c5" COLOR="#990000" CREATED="1710983365347" ID="ID_12713467" MODIFIED="1710986045325" TEXT="IterIndex_test">
<icon BUILTIN="pencil"/>
<node CREATED="1710983370851" ID="ID_929461554" MODIFIED="1710983390046" TEXT="verwende IterCursor_text als Vorlage">
<icon BUILTIN="idea"/>
<node CREATED="1710983391672" ID="ID_201237845" MODIFIED="1710983405226" TEXT="der deckt n&#xe4;mlich eine ganze Menge ekelhafte Randf&#xe4;lle mit ab"/>
<node CREATED="1710983406078" ID="ID_252133900" MODIFIED="1710983436747" TEXT="auch die const-correctness und State-cloning"/>
</node>
<node BACKGROUND_COLOR="#fdfdcf" COLOR="#ff0000" CREATED="1710986046845" ID="ID_1980706468" MODIFIED="1710986077126" TEXT="sollte noch eine smart-Ptr-Variante mit abdecken">
<icon BUILTIN="bell"/>
</node>
</node>
</node>
</node>
</node>
<node CREATED="1710856784967" ID="ID_201927694" MODIFIED="1710856798759" TEXT="Parsing soll eager sein (wegen Syntax-Fehlern)"/>
</node>
@ -120672,6 +120729,31 @@ class Something
</node>
</node>
</node>
<node CREATED="1710977317941" ID="ID_1453026433" MODIFIED="1710977322814" TEXT="std::string_view">
<node CREATED="1710977334174" ID="ID_1310001368" MODIFIED="1710977350088" TEXT="ist eine read-only-View in ein char-Array"/>
<node CREATED="1710977354168" ID="ID_184856921" MODIFIED="1710977365523" TEXT="ist explizit f&#xfc;r Performance-Optimierung gedacht"/>
<node BACKGROUND_COLOR="#e0ceaa" COLOR="#690f14" CREATED="1710977367862" ID="ID_860112408" MODIFIED="1710986482731" TEXT="Gefahren">
<linktarget COLOR="#7b415c" DESTINATION="ID_860112408" ENDARROW="Default" ENDINCLINATION="-3082;815;" ID="Arrow_ID_1628394674" SOURCE="ID_359874280" STARTARROW="None" STARTINCLINATION="-1036;64;"/>
<node CREATED="1710977372915" ID="ID_1575898732" MODIFIED="1710977488625" TEXT="dangling references">
<icon BUILTIN="clanbomber"/>
<node CREATED="1710977449251" ID="ID_1055400302" MODIFIED="1710977453942" TEXT="Lebensdauer der Basis-Daten beachten"/>
<node CREATED="1710977455010" ID="ID_402913842" MODIFIED="1710977485628" TEXT="verborgener Pointer: Gefahr bei Inline-Daten, die verschoben / realloziert werden"/>
</node>
<node CREATED="1710977381021" ID="ID_180009098" MODIFIED="1710977501175">
<richcontent TYPE="NODE"><html>
<head/>
<body>
<p>
Konversion string_view &#10236; string <b>kopiert</b>&#160;die Daten
</p>
</body>
</html></richcontent>
<icon BUILTIN="messagebox_warning"/>
<node CREATED="1710977502025" ID="ID_766667745" MODIFIED="1710977510502" TEXT="deshalb ist diese Konversion explizit"/>
<node CREATED="1710977511069" ID="ID_1874799796" MODIFIED="1710977520557" TEXT="(wor&#xfc;ber sich viele Leute aufgeregt haben)"/>
</node>
</node>
</node>
</node>
<node CREATED="1636143147825" ID="ID_224980157" MODIFIED="1636143159589" TEXT="Assembly">
<node CREATED="1636143161969" ID="ID_1119605136" MODIFIED="1636143179445" TEXT="r?x : 64-Bit-Register"/>