ichthyo/LUMIERA.clone
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Library: unable to reproduce the problem with an "equivalent" demo example

Browse source 
...the simplified demo variant in try.cpp is accepted by the compiler and works as intended,
while the seemingly equivalent construction in verb-visitor.hpp is rejected by the compiler

This discrepancy might lead to a solution....?
This commit is contained in:
Fischlurch 2019-04-22 17:45:38 +02:00
parent a530665769
commit 612a442550
2 changed files with 120 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

44
research/try.cpp
View file

@ -123,6 +123,39 @@ applyTuple (FUN& fun)
///////////////////////////TODO : Debugging
struct Trackr
{
size_t num;
Trackr (size_t val)
: num(val)
{
cout <<"Trackr("<<val<<")"<<endl;
}
~Trackr()
{
cout <<"~Trackr()"<<endl;
}
Trackr (Trackr const& lval)
: num(lval.num)
{
cout <<"Trackr()<<-LVal"<<endl;
}
Trackr (Trackr && rval)
: num(rval.num)
{
cout <<"Trackr()<<-RVal"<<endl;
}
Trackr&
operator= (Trackr const& orig)
{
cout <<"Tracker = orig"<<endl;
num = orig.num;
return *this;
}
};
///////////////////////////TODO : Debugging
int
@ -138,6 +171,17 @@ main (int, char**)
Hol holder(tup);
holder.applyTuple (fun);
auto trp = std::make_tuple(2u,Trackr(3));
auto frn = [](uint& x, Trackr y)
{
cout << x<<"*Trckr("<<y.num<<")="<<(x*y.num)<<endl;
};
using Hrl = Holder<decltype(frn), uint, Trackr>;
Hrl hrlder(trp);
hrlder.applyTuple (frn);
cout << "\n.gulp.\n";
return 0;
}

76
wiki/thinkPad.ichthyo.mm
View file

@ -19799,6 +19799,82 @@
</node>
</node>
</node>
<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1555947349235" ID="ID_599059144" MODIFIED="1555947358288" TEXT="L&#xf6;sung gesucht....">
<icon BUILTIN="flag-yellow"/>
<node CREATED="1555947359783" ID="ID_1366291443" MODIFIED="1555947366938" TEXT="noch schlimmer...">
<node CREATED="1555947367949" ID="ID_1145455475" MODIFIED="1555947477936" TEXT="auch die Textbook-Impl von std::apply funktioiniert genauso">
<richcontent TYPE="NOTE"><html>
<head>
</head>
<body>
<p>
d.h. std::get&lt;idx&gt; (std::forward&lt;TUP&gt; (tuple))
</p>
</body>
</html>
</richcontent>
</node>
<node CREATED="1555947482051" ID="ID_814853878" MODIFIED="1555947512633" TEXT="...und produziert den gleichen Compiler-Fehler">
<richcontent TYPE="NOTE"><html>
<head>
</head>
<body>
<p>
wenn ich das Tupel als Referenz anliefere
</p>
</body>
</html>
</richcontent>
</node>
</node>
<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1555947514403" ID="ID_1459759406" MODIFIED="1555947533813" TEXT="Kann den Fehler isoliert nicht nachstellen">
<icon BUILTIN="forward"/>
<node CREATED="1555947535499" ID="ID_218400480" MODIFIED="1555947537990" TEXT="try.cpp"/>
<node CREATED="1555947538554" ID="ID_1700362760" MODIFIED="1555947549232" TEXT="&quot;sinngem&#xe4;&#xdf;&quot; nachgebaut"/>
<node CREATED="1555947549617" ID="ID_386072993" MODIFIED="1555947560899" TEXT="das compiliert problemlos"/>
<node CREATED="1555947561535" ID="ID_858467762" MODIFIED="1555947660539" TEXT="und macht LValue-Initialisierung">
<richcontent TYPE="NOTE"><html>
<head>
</head>
<body>
<p>
...sichtbar wenn man ein Trackr-Objekt
</p>
<p>
als value-Parameter auf der Zielfunktion verwendet.
</p>
<p>
</p>
<p>
Im extrahierten Beispiel wird das LValue-copy-initialisiert
</p>
<p>
wohingegen im realen code, wo auch das std::forward(tuple) dabei ist,
</p>
<p>
der betreffende Wert dann RValue-Initialisiert wird, d.h. dabei das betreffende Tupel-Element konsumiert
</p>
</body>
</html>
</richcontent>
</node>
<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1555947661358" ID="ID_917133929" MODIFIED="1555947677634" TEXT="Ich seh den Unterschied nicht">
<icon BUILTIN="smily_bad"/>
<node CREATED="1555947705866" ID="ID_139554682" MODIFIED="1555947737849" TEXT="warum akzeptiert der Compiler die korrekte variante im realen Code nicht??"/>
<node CREATED="1555947747068" ID="ID_1646796994" MODIFIED="1555947794848" TEXT="f&#xfc;r micht sind beide Varianten (try.cpp und verb-visitor.hpp) &#xe4;quivaltent"/>
<node CREATED="1555947795281" ID="ID_1250854173" MODIFIED="1555947806627" TEXT="f&#xfc;r den Compiler anscheinend nicht">
<icon BUILTIN="idea"/>
<node BACKGROUND_COLOR="#fdfdcf" COLOR="#ff0000" CREATED="1555947814658" ID="ID_1580965808" MODIFIED="1555947822428" TEXT="das k&#xf6;nne ein Ansatzpunkt sein">
<icon BUILTIN="flag-pink"/>
</node>
</node>
</node>
</node>
</node>
</node>
<node CREATED="1555807238238" ID="ID_383098394" MODIFIED="1555807261859" TEXT="Copy-Support von PolymorphicValue ist &quot;komisch&quot;">
<node CREATED="1555807266221" ID="ID_262959695" MODIFIED="1555807278396" TEXT="nach heutigem Stand: unbeholfen implementiert"/>