tuple-helper.hpp

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/*
  TUPLE-HELPER.hpp  -  metaprogramming utilities for type and data tuples

   Copyright (C)
     2016,            Hermann Vosseler <Ichthyostega@web.de>

  **Lumiera** 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. See the file COPYING for further details.

*/


#ifndef LIB_META_TUPLE_HELPER_H
#define LIB_META_TUPLE_HELPER_H

#include "lib/meta/typelist.hpp"
#include "lib/meta/typelist-util.hpp"
#include "lib/meta/typeseq-util.hpp"
#include "lib/meta/variadic-helper.hpp"
#include "lib/meta/util.hpp"

#include <tuple>
#include <utility>


namespace util { // forward declaration
  
  template<typename TY>
  std::string
  toString (TY const& val)  noexcept;
}


namespace lib {
namespace meta {
  
  template<typename T>
  struct is_Tuple
    : std::false_type
    { };
  
  template<typename...TYPES>
  struct is_Tuple<std::tuple<TYPES...>>
    : std::true_type
    { };
  
  template<typename...TYPES>
  struct is_Tuple<const std::tuple<TYPES...>>
    : std::true_type
    { };

  template<class TUP>
  using enable_if_Tuple = lib::meta::enable_if<lib::meta::is_Tuple<std::remove_reference_t<TUP>>>;

  template<class TUP>
  using disable_if_Tuple = lib::meta::disable_if<lib::meta::is_Tuple<std::remove_reference_t<TUP>>>;
  
  
  template<class TUP, class FUN, typename = enable_if_Tuple<TUP>>
  void
  forEach (TUP&& tuple, FUN fun)
  {
           std::apply ([&fun](auto&&... elms)
                            {
                              (fun (std::forward<decltype(elms)> (elms)), ...);
                            }
                      ,std::forward<TUP> (tuple));
  }
  
  template<class TUP, class FUN, typename = enable_if_Tuple<TUP>>
  auto
  mapEach (TUP&& tuple, FUN fun)
  {
    return std::apply ([&fun](auto&&... elms)
                            {  //..construct the type explicitly (make_tuple would decay fun result types)
                              using Tuple = std::tuple<decltype(fun (std::forward<decltype(elms)> (elms))) ...>;
                              return Tuple (fun (std::forward<decltype(elms)> (elms)) ...);
                            }
                      ,std::forward<TUP> (tuple));
  }
  
  
  
  
  
  namespace { // rebinding helper to create std::tuple from a type sequence
    
    template<typename SEQ>
    struct BuildTupleType
      : std::false_type
      { };
    
    template<typename...TYPES>
    struct BuildTupleType<TySeq<TYPES...>>
      {
        using Type = std::tuple<TYPES...>;
      };
    
    template<typename...TYPES>
    struct BuildTupleType<Types<TYPES...>>
      {
        using VariadicSeq = typename StripNullType<Types<TYPES...>>::Seq;
        
        using Type = typename BuildTupleType<VariadicSeq>::Type;
      };
    
    template<class H, typename TAIL>
    struct BuildTupleType<Node<H, TAIL>>
      {
        using Seq  = typename Types< Node<H,TAIL>>::Seq;
        using Type = typename BuildTupleType<Seq>::Type;
      };
    
    template<>
    struct BuildTupleType<NullType>
      {
        using Type = typename BuildTupleType<Types<>>::Type;
      };
  }
  
  
  template<typename TYPES>
  using Tuple = typename BuildTupleType<TYPES>::Type;
  
  
  using std::tuple_size;
  using std::tuple_element;
  
  
  
  template<typename...TYPES>
  struct RebindTupleTypes
    {
      using Seq  = typename Types<TYPES...>::Seq;
      using List = typename Seq::List;
    };
  template<typename...TYPES>
  struct RebindTupleTypes<std::tuple<TYPES...>>
    {
      using Seq  = typename Types<TYPES...>::Seq;
      using List = typename Seq::List;
    };
  
  
  
  
  
  
  
  template< typename TYPES
          , template<class,class, size_t> class _ElmMapper_
          >
  struct TupleConstructor
    : Tuple<TYPES>
    {
      using SequenceIterator = typename BuildIdxIter<TYPES>::Ascending;
      
    protected:
      template<class SRC, size_t...idx>
      TupleConstructor (SRC values, IndexSeq<idx...>)
        : Tuple<TYPES> (_ElmMapper_<SRC, Tuple<TYPES>, idx>{values}...)
        { }
      
      
    public:
      template<class SRC>
      TupleConstructor (SRC values)
        : TupleConstructor (values, SequenceIterator())
        { }
    };
  
  
  template<class SRC, class TAR>
  struct ElementExtractor;
  

  template<class SRC, class TAR, size_t i>
  using ExtractArg = typename ElementExtractor<SRC, TAR>::template Access<i>;
  
  
  template<typename TYPES, class SRC>
  Tuple<TYPES>
  buildTuple (SRC values)
  {
    return TupleConstructor<TYPES, ExtractArg> (values);
  }


  
  
  
  
  
  
  template
    < template<class,class,class, uint> class _X_   
    , typename TYPES                                
    , class TUP =Tuple<TYPES>                       
    , uint i = 0                                    
    >
  class BuildTupleAccessor
    {
      // prepare recursion...
      using Head         = typename Split<TYPES>::Head;
      using Tail         = typename Split<TYPES>::Tail;
      using NextBuilder  = BuildTupleAccessor<_X_, Tail,TUP, i+1>;
      using NextAccessor = typename NextBuilder::Product;
    public:
      
      using Product = _X_< Head            // the type to use for this accessor
                         , NextAccessor    // the base type to inherit from
                         , TUP             // the tuple type we build upon
                         , i               // current element index
                         >;
    };
  
  
  template
    < template<class,class,class, uint> class _X_
    , class TUP
    , uint i
    >
  class BuildTupleAccessor< _X_, Types<>, TUP, i>
    {
    public:
      using Product = _X_<NullType, TUP, TUP, i>;   // Note: i == tuple size
      
    };
  
  
  
  template
    < typename TY
    , class BASE
    , class TUP
    , uint idx
    >
  struct TupleElementDisplayer
    : BASE
    {
      using BASE::BASE;
      
      std::string
      dump (std::string const& prefix ="(")  const
        {
          return BASE::dump (prefix + util::toString(std::get<idx>(*this))+",");
        }
    };
  
  template<class TUP, uint n>
  struct TupleElementDisplayer<NullType, TUP, TUP, n>
    : TUP
    {
      TupleElementDisplayer (TUP const& tup)
        : TUP(tup)
        { }
      
      std::string
      dump (std::string const& prefix ="(")  const
        {
          if (1 < prefix.length())
            // remove the trailing comma
            return prefix.substr (0, prefix.length()-1) +")";
          else
            return prefix+")";
        }
    };
  
  
  template<typename...TYPES>
  inline std::string
  dump (std::tuple<TYPES...> const& tuple)
  {
    using BuildAccessor = BuildTupleAccessor<TupleElementDisplayer, Types<TYPES...>>;
    using Displayer     = typename BuildAccessor::Product ;
    
    return static_cast<Displayer const&> (tuple)
          .dump();
  }
  
  
  
}} // namespace lib::meta


// add a specialisation to enable tuple string conversion
namespace util {
  
  template<typename...TYPES>
  struct StringConv<std::tuple<TYPES...>>
    {
      static std::string
      invoke (std::tuple<TYPES...> const& tuple) noexcept
        try {
          return "«"+typeStr(tuple)
               + "»──" + lib::meta::dump (tuple);
        }
        catch(...) { return FAILURE_INDICATOR; }
    };
  
  
} // namespace util
#endif /*LIB_META_TUPLE_HELPER_H*/