clean-up: define variadic type-sequences independently

To bootstrap this tricky refactoring, initially a bridge definition
was used, with a variadic argument pack, but delegating to the old
non-variadic type sequence and from there further into LISP style
list processing of types and meta definitions, as pioneered by the
Loki libarary. Luimiera uses this technique since a long time to
perform the complex tasks sometimes required for code generation
and generic function and type adaptation.

with this changeset, a direct variadics based entrance into
type list processing is provided, so that the old definition
is now completely separate and can be removed eventually.

src/lib/meta/tuple-helper.hpp

@@ -162,14 +162,14 @@ namespace meta {
     template<class H, typename TAIL>
     struct BuildTupleType<Node<H, TAIL>>
       {
-        using Seq  = typename TyOLD< Node<H,TAIL>>::Seq;
+        using Seq  = typename TySeq<Node<H,TAIL>>::Seq;
         using Type = typename BuildTupleType<Seq>::Type;
       };
     
     template<>
     struct BuildTupleType<Nil>
       {
-        using Type = typename BuildTupleType<TyOLD<>>::Type;
+        using Type = std::tuple<>;
       };
   }
   

src/lib/meta/typelist.hpp

@@ -31,22 +31,32 @@ This code is heavily inspired by
 
 /** @file typelist.hpp
  ** A template metaprogramming technique for manipulating collections of types.
- ** Effectively this is a tailored and simplified version of what can be found in the Loki library.
+ ** - **Type Sequences** are used to transport a variadic sequence of types
- ** We use it in other generic library-style code to generate repetitive code.
+ ** - **Type Lists** (»Loki style«) can be created from a type sequence and
+ **   represent the same information by _nodes_ with _head_ and _tail_.
+ ** The latter brings LISP style recursive manipulation techniques into the
+ ** realm of type metaprogramming; this approach was pioneered with the
+ ** **Loki Library** by Alexandrescu (2001) and makes complex processing
+ ** much easier to write  and to understand following. Effectively the set
+ ** of definitions used here is a tailored version of what could be found
+ ** in the Loki library, and was in the following years integrated with
+ ** processing of variadics, function manipulation and std::tuple.
+ ** This framework is typically used to generate repetitive code,
+ ** based on a collection of types, with type-specific adaptations.
  ** @remark If you tend to find the use of template metaprogramming detrimental
  **         (or functional programming and generally any kind of abstraction)
  **         please kindly ignore the technical details and just consider the
  **         benefit of simplification for the client code.
  ** 
- ** Interface for using this facility is the template `Types<TS...>`.
+ ** Interface for using this facility is the template `Types<TS...>` (the type sequence).
  ** To start typelist processing, other templates typically pick up the Types<...>::List type.
  ** This allows for LISP-style list processing, with a pattern match on either `Node<TY,TYPES>`
  ** or the type `Nil` to terminate recursion. In C++ template metaprogramming, "pattern match"
  ** is done by partial template specialisations (the compiler will pick up and thus
- ** match the template parameters). A typedef acts like a declaration in normal
+ ** match the template parameters). A type definition acts like a variable declaration
- ** programming. Because such a "declaration" can't be changed after the fact,
+ ** in regular programming. Because such a "declaration" can't be changed after the fact,
- ** effectively this is a flavour of functional programming. Just the
+ ** effectively this is a flavour of functional programming; the _execution environment_
- ** "execution environment" is the compiler, during compilation.
+ ** is the compiler, and evaluation is set off by some template instantiation.
  ** 
  ** @warning the metaprogramming part of Lumiera to deal with type sequences is in a
  **          state of transition, since C++11 now offers direct language support for
@@ -59,10 +69,12 @@ This code is heavily inspired by
  **          since the latter can only be rebound through pattern matching.
  ** @todo transition lib::meta::Types to variadic parameters  /////////////////////////////////TICKET #987
  ** 
- ** @see lib::visitor::Applicable usage example
- ** @see control::CommandSignature more elaborate usage example (dissecting a functor signature)
  ** @see TypeList_test
  ** @see TypeListManip_test
+ ** @see TypeSecManip_test
+ ** @see function.hpp
+ ** @see tuple-helper.hpp
+ ** @see variadic-helper.hpp
  ** 
  */
 
@@ -75,24 +87,28 @@ This code is heavily inspired by
 
 namespace lib {
 namespace meta {
-    
+  
-    struct Nil
+  /** »Empty« mark */
-      {
+  struct Nil
-        using List = Nil;
+    {
-      };
+      using List = Nil;
-    
+    };
-    template<class H, class T>
+  
-    struct Node
+  /** Type list with head and tail;
-      {
+   *  T ≡ Nil marks list end. */
-        using List = Node;
+  template<class H, class T>
-        using Head = H;
+  struct Node
-        using Tail = T;
+    {
-      };
+      using List = Node;
-    
+      using Head = H;
-    using NilNode = Node<Nil,Nil>;
+      using Tail = T;
-    
+    };
-    
+  
-    
+  using NilNode = Node<Nil,Nil>;
+  
+  
+  
+   //////////////////////////////////////////////////////////////////////////////////////////////////////////TICKET #987 : this is the old non-variadic definition from lib Loki -- it will be obsoleted with the transition
     template
       < class T01=Nil
       , class T02=Nil
@@ -135,7 +151,7 @@ namespace meta {
       };
     
     
-   //////////////////////////////////////////////////////////////////////////////////////////////////////////TICKET #987 temporary WORKAROUND -- to be obsoleted
+   //////////////////////////////////////////////////////////////////////////////////////////////////////////TICKET #987 temporary WORKAROUND -- transition to variadic type-sequences
   /**
    * temporary workaround:
    * alternative definition of "type sequence",
@@ -147,13 +163,26 @@ namespace meta {
    *    entries do not play well with other variadic defs.
    * @deprecated when we switch our primary type sequence type
    *    to variadic parameters, this type will be obsoleted.             ////////////////////////////////////TICKET #987 : make lib::meta::Types<TYPES...> variadic
+   * @todo 6/25 the transition is now mostly settled
+   *       and will be completed by just _renaming_ this
+   *       definition back into `Types<...>`
    */
   template<typename...TYPES>
-  struct TySeq
+  struct TySeq;
+  
+  template<typename T, typename...TS>
+  struct TySeq<T,TS...>
     {
-      using Seq = TySeq;
+      using List = Node<T, typename TySeq<TS...>::List>;
-      using List = typename TyOLD<TYPES...>::List;
+      using Seq  = TySeq;
     };
-   //////////////////////////////////////////////////////////////////////////////////////////////////////////TICKET #987 temporary WORKAROUND(End) -- to be obsoleted
+  
+  template<>
+  struct TySeq<>
+    {
+      using List = Nil;
+      using Seq  = TySeq<>;
+    };
+  
 }} // namespace lib::meta
 #endif

src/lib/meta/typeseq-util.hpp

@@ -172,7 +172,7 @@ namespace meta {
   struct Prepend<T, TySeq<TYPES...>>
   {
     using Seq  = TySeq<T, TYPES...>;
-    using List = typename TyOLD<T, TYPES...>::List;
+    using List = typename TySeq<T, TYPES...>::List;
   };
   
   
@@ -195,6 +195,10 @@ namespace meta {
       using List = Nil;
       using Seq  = TySeq<>;
     };
+  template<>
+  struct TySeq<NilNode>
+    : TySeq<Nil>
+    { };
   
   
    //////////////////////////////////////////////////////////////////////////////////////////////////////////TICKET #987 temporary WORKAROUND -- to be obsoleted
@@ -338,19 +342,18 @@ namespace meta {
   template<class TYPES, uint i=1>
   class Shifted
     {
-      typedef typename Split<TYPES>::Tail Tail;
+      using Tail = typename Split<TYPES>::Tail;
     public:
-      typedef typename Shifted<Tail,i-1>::Type Type;
+      using Type = typename Shifted<Tail,i-1>::Type;
-      typedef typename Split<Type>::Head       Head;
+      using Head = typename Split<Type>::Head;
     };
   
   template<class TYPES>
   struct Shifted<TYPES,0>
     {
-      typedef TYPES                      Type;
+      using Type = TYPES;
-      typedef typename Split<Type>::Head Head;
+      using Head = typename Split<Type>::Head;       ///< @warning may be Nil in case of an empty list
     };
-                          ///////////////////////////////////////////////////////////////////////////////////TICKET #987 : reimplement for variadic type-sequences
   
   
   

tests/library/meta/typelist-diagnostics.hpp

@@ -112,7 +112,7 @@ namespace meta {
       struct Printer<Nil, BASE>
         : BASE
         {
-          static string show() { return _Fmt("-<%u>%s") % "·" % BASE::show(); }
+          static string show() { return _Fmt("-<%s>%s") % "·" % BASE::show(); }
         };
       
       template<class BASE, int I>
@@ -133,19 +133,19 @@ namespace meta {
       struct Printer<int, BASE>  ///< display the presence of a plain int in the typelist
         : BASE
         {
-          static string show() { return _Fmt("-<%u>%s") % 'i' % BASE::show(); }
+          static string show() { return _Fmt("-<%s>%s") % 'i' % BASE::show(); }
         };
       
       
       
       /** call the debug-print for a typelist
        *  utilising the Printer template */
-      template<class L>
+      template<class LIST>
       string
       printSublist ()
       {
-        typedef InstantiateChained<L, Printer, NullP> SubList;
+        using PrinterChain = InstantiateChained<LIST, Printer, NullP>;
-        return SubList::show();
+        return PrinterChain::show();
       }
       
       /** Specialisation for debug-printing of a nested sublist */
@@ -184,8 +184,8 @@ namespace meta {
     string                  >
     showType ()
     {
-      typedef InstantiateChained<typename TYPES::List, Printer, NullP>  DumpPrinter;
+      using TypeList = typename TYPES::List;
-      return DumpPrinter::show();
+      return printSublist<TypeList>();
     }
     
     //  Note: we define overloads of this function for other types, especially Tuples

tests/library/meta/typelist-manip-test.cpp

@@ -172,8 +172,8 @@ namespace test {
               using NilSplit = PickLast<Nil>::Type;
               using NilList  = PickLast<Nil>::List;
               
-              EXPECT (TySeq<NilSplit>, "-");
+              EXPECT (NilSplit, "-");
-              EXPECT (NilList        , "-");
+              EXPECT (NilList , "-");
             }
           
           

tests/library/meta/typeseq-manip-test.cpp

@@ -136,7 +136,8 @@ namespace test {
           using Head_3 = TySeq<Shifted<Seq,3>::Head>;  EXPECT (Head_3, "-<1>-");
           using Head_4 = TySeq<Shifted<Seq,4>::Head>;  EXPECT (Head_4, "-<2>-");
           using Head_5 = TySeq<Shifted<Seq,5>::Head>;  EXPECT (Head_5, "-<3>-");
-          using Head_6 = TySeq<Shifted<Seq,6>::Head>;  EXPECT (Head_6, "-");
+          using Head_6 = TySeq<Shifted<Seq,6>::Head>;  EXPECT (Head_6, "-"    );
+          using Head_7 = TySeq<Shifted<Seq,7>::Head>;  EXPECT (Head_7, "-"    );
         }
       
       
@@ -155,7 +156,10 @@ namespace test {
           using Head   = Split<Seq>::Head;
           using End    = Split<Seq>::End;
           
-          using HeadEnd = TySeq<Head,End>;      EXPECT (HeadEnd, "-<1>-<9>-");
+          using Ends   = TySeq<Head,End>;       EXPECT (Ends  , "-<1>-<9>-");
+          
+          using NoList = Split<TySeq<>>::List;  EXPECT (NoList, "-");
+          using NoHead = Split<TySeq<>>::Head;  EXPECT (NoHead, "-");
         }
       
       

wiki/thinkPad.ichthyo.mm

@@ -164238,6 +164238,21 @@ Since then others have made contributions, see the log for the history.</font></
 </node>
 </node>
 <node COLOR="#435e98" CREATED="1748828247849" ID="ID_476644412" MODIFIED="1748869713383" TEXT="Verbindung mit Typelisten">
+<node COLOR="#338800" CREATED="1749001830758" ID="ID_91346918" MODIFIED="1749007560980" TEXT="eigenst&#xe4;ndige Konstruktion von Type-Listen hinzuf&#xfc;gen">
+<richcontent TYPE="NOTE"><html>
+  <head>
+    
+  </head>
+  <body>
+    <p>
+      bisher wurde das durch Delegieren an die alte Loki-Implementierung bewerkstelligt; das nun direkt auf der Basis von Variadics zu machen, w&#228;re der zentrale Schritt, der das neue &#214;kosystem der variadischen Typlisten autonom macht (so da&#223; man am Ende die alte nicht-variadische Definition entfernen kann)
+    </p>
+  </body>
+</html>
+</richcontent>
+<arrowlink COLOR="#8ec9a3" DESTINATION="ID_1097523075" ENDARROW="Default" ENDINCLINATION="1324;0;" ID="Arrow_ID_370033957" STARTARROW="None" STARTINCLINATION="481;24;"/>
+<icon BUILTIN="button_ok"/>
+</node>
 <node COLOR="#435e98" CREATED="1748828313009" ID="ID_1470463237" MODIFIED="1748869832016" TEXT="R&#xfc;ckweg Typelist &#x27f6; Typsequenz">
 <arrowlink DESTINATION="ID_281104576" ENDARROW="Default" ENDINCLINATION="589;-82;" ID="Arrow_ID_351374746" STARTARROW="None" STARTINCLINATION="458;41;"/>
 <node CREATED="1748828416378" ID="ID_1994646495" MODIFIED="1748869656471" TEXT="es gibt eine Spezialisierung von TyOLD">
@@ -164274,12 +164289,12 @@ Since then others have made contributions, see the log for the history.</font></
 <font NAME="SansSerif" SIZE="10"/>
 </node>
 </node>
-<node CREATED="1748828920169" ID="ID_511778446" MODIFIED="1748869770714" TEXT="generator.hpp arbeitet ebenfalls nur auf Typlisten">
+<node COLOR="#435e98" CREATED="1748828920169" ID="ID_511778446" MODIFIED="1749003965023" TEXT="generator.hpp arbeitet ebenfalls nur auf Typlisten">
 <arrowlink DESTINATION="ID_803058969" ENDARROW="Default" ENDINCLINATION="852;0;" ID="Arrow_ID_1971292758" STARTARROW="None" STARTINCLINATION="302;17;"/>
 <node CREATED="1748828953483" ID="ID_1328523415" MODIFIED="1748828958980" TEXT="das kommt mir nun zugute"/>
 <node CREATED="1748828933676" ID="ID_1716238563" MODIFIED="1748828952655" TEXT="man k&#xf6;nnte dann convenience-Front-End definieren"/>
 </node>
-<node CREATED="1748828754106" ID="ID_138237629" MODIFIED="1748869733060" TEXT="typelist-diagnostic ebenso">
+<node COLOR="#435e98" CREATED="1748828754106" ID="ID_138237629" MODIFIED="1749003967494" TEXT="typelist-diagnostic ebenso">
 <node CREATED="1748828767089" ID="ID_1047311703" MODIFIED="1748828818895" TEXT="meta::is_Typelist ist geschickt definiert">
 <richcontent TYPE="NOTE"><html>
   <head>
@@ -164309,17 +164324,19 @@ Since then others have made contributions, see the log for the history.</font></
 </node>
 </node>
 </node>
-<node CREATED="1748829095135" ID="ID_1295682918" MODIFIED="1748829098145" TEXT="Funktionen">
+<node COLOR="#435e98" CREATED="1748829095135" ID="ID_1295682918" MODIFIED="1749007403090" TEXT="Funktionen">
-<node CREATED="1748829099022" ID="ID_766756688" MODIFIED="1748829101916" TEXT="Signatur-Utils">
+<node COLOR="#435e98" CREATED="1748829099022" ID="ID_766756688" MODIFIED="1749007398648" TEXT="Signatur-Utils">
 <node CREATED="1748829959670" ID="ID_1188075291" MODIFIED="1748829968228" TEXT="sind bereits mit beiden kompatibel"/>
 </node>
-<node CREATED="1748829102455" ID="ID_1254282139" MODIFIED="1748829106392" TEXT="Closure">
+<node COLOR="#338800" CREATED="1748829102455" ID="ID_1254282139" MODIFIED="1749007395415" TEXT="Closure">
-<node CREATED="1748829838133" ID="ID_1933174501" MODIFIED="1748829845923" TEXT="hat nur wenige Verwendungen">
+<icon BUILTIN="button_ok"/>
+<node CREATED="1748829838133" ID="ID_1933174501" MODIFIED="1748995159628" TEXT="wenige wichtige Verwendungen">
 <node CREATED="1748829860803" ID="ID_517247632" MODIFIED="1748829863739" TEXT="Commands"/>
 <node CREATED="1748829872320" ID="ID_568804131" MODIFIED="1748829875428" TEXT="Random-Draw"/>
 <node CREATED="1748829881837" ID="ID_1354679657" MODIFIED="1748829885400" TEXT="tuple-closure"/>
 <node CREATED="1748829890844" ID="ID_1803577911" MODIFIED="1748829894782" TEXT="view-spec-dsl"/>
 </node>
+<node CREATED="1749007506535" ID="ID_240022720" MODIFIED="1749007506535" TEXT="mu&#xdf; auf einen Schlag geschwenkt werden (Komplexit&#xe4;t)"/
 <node CREATED="1748829733384" ID="ID_83679265" MODIFIED="1748829744922" TEXT="sollte sich bereits ohne weiteres schwenken lassen"/>
 <node CREATED="1748829745682" ID="ID_61352432" MODIFIED="1748829759664" TEXT="erzeugt nur Tuple, oder macht Split / Prepend"/>
 <node CREATED="1748829779637" ID="ID_1158113558" MODIFIED="1748829835939" TEXT="man k&#xf6;nnte dann im Nachgang die Apply-Definition eliminieren">
@@ -164394,7 +164411,7 @@ Since then others have made contributions, see the log for the history.</font></
 <node CREATED="1748829468217" MODIFIED="1748829468217" TEXT="SessionServiceAccess_test"/>
 <node CREATED="1748829480048" MODIFIED="1748829480048" TEXT="FunctionClosure_test"/>
 <node CREATED="1748829502213" MODIFIED="1748829502213" TEXT="FunctionComposition_test"/>
-<node CREATED="1748829512571" MODIFIED="1748829512571" TEXT="GeneratorCombinations_test"/>
+<node COLOR="#435e98" CREATED="1748829512571" ID="ID_1542151497" MODIFIED="1749007468620" TEXT="GeneratorCombinations_test"/>
 <node COLOR="#435e98" CREATED="1748829523737" ID="ID_803058969" MODIFIED="1748883754992" TEXT="TypeListGenerator_test">
 <linktarget COLOR="#a9b4c1" DESTINATION="ID_803058969" ENDARROW="Default" ENDINCLINATION="852;0;" ID="Arrow_ID_1971292758" SOURCE="ID_511778446" STARTARROW="None" STARTINCLINATION="302;17;"/>
 </node>
@@ -164415,7 +164432,9 @@ Since then others have made contributions, see the log for the history.</font></
 <node COLOR="#435e98" CREATED="1748829576396" ID="ID_281104576" MODIFIED="1748883754992" TEXT="TypeListUtil_test">
 <linktarget COLOR="#a9b4c1" DESTINATION="ID_281104576" ENDARROW="Default" ENDINCLINATION="589;-82;" ID="Arrow_ID_351374746" SOURCE="ID_1470463237" STARTARROW="None" STARTINCLINATION="458;41;"/>
 </node>
-<node CREATED="1748829567920" ID="ID_1097523075" MODIFIED="1748959903101" TEXT="TypeList_test"/>
+<node COLOR="#435e98" CREATED="1748829567920" ID="ID_1097523075" MODIFIED="1749007565198" TEXT="TypeList_test">
+<linktarget COLOR="#8ec9a3" DESTINATION="ID_1097523075" ENDARROW="Default" ENDINCLINATION="1324;0;" ID="Arrow_ID_370033957" SOURCE="ID_91346918" STARTARROW="None" STARTINCLINATION="481;24;"/>
+</node>
 <node CREATED="1748829607017" MODIFIED="1748829607017" TEXT="Variant_test"/>
 </node>
 </node>