iter-adapter.hpp

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/*
  ITER-ADAPTER.hpp  -  helpers for building simple forward iterators

  Copyright (C)         Lumiera.org
    2009,               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.

*/

#ifndef LIB_ITER_ADAPTER_H
#define LIB_ITER_ADAPTER_H


#include "lib/error.hpp"
#include "lib/meta/value-type-binding.hpp"

#include <iterator>


namespace lib {
  
  
  namespace { // internal helpers
    inline void
    _throwIterExhausted()
    {
      throw lumiera::error::Invalid ("Can't iterate further",
            lumiera::error::LUMIERA_ERROR_ITER_EXHAUST);
    }
  }
  
#define ENABLE_USE_IN_STD_RANGE_FOR_LOOPS(ITER)                              \
      friend ITER   begin (ITER const& it){ return it; }                      \
      friend ITER&& begin (ITER&& it)     { return static_cast<ITER&&> (it); } \
      friend ITER   end   (ITER const&)   { return ITER(); }                    \
      using iterator_category = std::input_iterator_tag;                         \
      using difference_type = size_t;

#define LIFT_PARENT_INCREMENT_OPERATOR(_BASECLASS_)\
      auto&                       \
      operator++()                 \
        {                           \
          _BASECLASS_::operator++(); \
          return *this;               \
        }
  
  

  template<class POS, class CON>
  class IterAdapter
    {
      CON source_;
      mutable POS pos_;
      
      using _ValTrait = meta::ValueTypeBinding<std::remove_pointer_t<POS>>;
      
    public:
      using value_type = typename _ValTrait::value_type;
      using reference = typename _ValTrait::reference;
      using pointer = typename _ValTrait::pointer;
      
      
      IterAdapter (CON src, POS const& startpos)
        : source_(src)
        , pos_(startpos)
        {
          check();
        }
      
      IterAdapter ()
        : source_()
        , pos_()
        { }
      
      explicit
      operator bool() const
        {
          return isValid();
        }
      
      
      /* === lumiera forward iterator concept === */
      
      reference
      operator*() const
        {
          _maybe_throw();
          return *pos_;
        }
      
      pointer
      operator->() const
        {
          _maybe_throw();
          return & *pos_;
        }
      
      IterAdapter&
      operator++()
        {
          _maybe_throw();
          iterate();
          return *this;
        }
      
      bool
      isValid ()  const
        {
          return check();
        }
      
      bool
      empty ()    const
        {
          return not isValid();
        }
      
      
    protected: /* === iteration control interface === */
      
      bool
      check()  const
        {
          return source_ && checkPoint (source_,pos_);           // extension point: free function checkPoint(...)
        }
      
      void
      iterate()
        {
          iterNext (source_,pos_);                               // extension point: free function iterNext(...)
          check();
        }    // checkPoint() might mark end condition
            //  for comparison with IterAdapter{}
      
      
      
    protected:
      using ConRef = typename meta::RefTraits<CON>::Reference;
      
      ConRef       source()       { return                source_; }
      const ConRef source() const { return unConst(this)->source_; }
      
      void
      resetPos (POS otherPos)                                    
        {
          pos_ = otherPos;
          check();
        }
      
    private:
      void
      _maybe_throw()  const
        {
          if (not isValid())
            _throwIterExhausted();
        }
      
      
    public:
      ENABLE_USE_IN_STD_RANGE_FOR_LOOPS (IterAdapter);
      
      template<class P1, class P2, class CX>
      friend bool operator== (IterAdapter<P1,CX> const&, IterAdapter<P2,CX> const&);
    };
  
  
  template<class P1, class P2, class CON>
  inline bool operator== (IterAdapter<P1,CON> const& il, IterAdapter<P2,CON> const& ir)  { return il.pos_ == ir.pos_; }
  
  template<class P1, class P2, class CON>
  inline bool operator!= (IterAdapter<P1,CON> const& il, IterAdapter<P2,CON> const& ir)  { return not (il == ir); }
  
  
  

  template<typename T, class ST =T>
  class IterStateWrapper
    {
      ST core_;
      
    public:
      typedef T* pointer;
      typedef T& reference;
      typedef T  value_type;
      
      IterStateWrapper (ST&& initialState)
        : core_(std::forward<ST>(initialState))
        { }
      
      IterStateWrapper (ST const& initialState)
        : core_(initialState)
        { }
      
      IterStateWrapper ()
        : core_()
        { }
      
      explicit
      operator bool() const
        {
          return isValid();
        }
      
      
      /* === lumiera forward iterator concept === */
      
      reference
      operator*() const
        {
          __throw_if_empty();
          return core_.yield();      // core interface: yield
        }
      
      pointer
      operator->() const
        {
          __throw_if_empty();
          return & core_.yield();    // core interface: yield
        }
      
      IterStateWrapper&
      operator++()
        {
          __throw_if_empty();
          core_.iterNext();          // core interface: iterNext
          return *this;
        }
      
      bool
      isValid ()  const
        {
          return core_.checkPoint(); // core interface: checkPoint
        }
      
      bool
      empty ()    const
        {
          return not isValid();
        }
      
    protected:
      
      ST &      stateCore()       { return core_; }
      ST const& stateCore() const { return core_; }
      
      void
      __throw_if_empty()  const
        {
          if (not isValid())
            _throwIterExhausted();
        }
      
      
      
    public:
      ENABLE_USE_IN_STD_RANGE_FOR_LOOPS (IterStateWrapper);
      
      template<class T1, class T2, class STX>
      friend bool operator== (IterStateWrapper<T1,STX> const&, IterStateWrapper<T2,STX> const&);
    };
  
  
  
  template<class T1, class T2, class ST>
  inline bool
  operator== (IterStateWrapper<T1,ST> const& il, IterStateWrapper<T2,ST> const& ir)
  {
    return (il.empty()   and ir.empty())
        or (il.isValid() and ir.isValid() and il.core_ == ir.core_);
  }
  
  template<class T1, class T2, class ST>
  inline bool
  operator!= (IterStateWrapper<T1,ST> const& il, IterStateWrapper<T2,ST> const& ir)
  {
    return not (il == ir);
  }
  
  
  
  
  template<class IT>
  class IterStateCore
    : public IT
    {
      static_assert (lib::meta::can_IterForEach<IT>::value
                    ,"Lumiera Iterator required as source");
    protected:
      IT&
      srcIter()  const
        {
          return unConst(*this);
        }
      
    public:
      using IT::IT;
      
      /* === state protocol API for IterStateWrapper === */
      bool
      checkPoint()  const
        {
          return bool(srcIter());
        }
      
      typename IT::reference
      yield()  const
        {
          return *srcIter();
        }
      
      void
      iterNext()
        {
          ++ srcIter();
        }
    };
  
  
  
  template<class COR>
  class CheckedCore
    : public COR
    {
      static_assert (lib::meta::is_StateCore<COR>::value
                    ,"Adapted type must expose a »state core« API");
    protected:
      COR&
      _rawCore()  const
        {
          return unConst(*this);
        }
      
      void
      __throw_if_empty()  const
        {
          if (not checkPoint())
            _throwIterExhausted();
        }
      
    public:
      template<typename...ARGS>
      CheckedCore (ARGS&& ...init)
        : COR(std::forward<ARGS>(init)...)
        { }
      
      CheckedCore()                               =default;
      CheckedCore (CheckedCore&&)                 =default;
      CheckedCore (CheckedCore const&)            =default;
      CheckedCore& operator= (CheckedCore&&)      =default;
      CheckedCore& operator= (CheckedCore const&) =default;
      
      
      /* === state protocol API for IterStateWrapper === */
      bool
      checkPoint()  const
        {
          return _rawCore().checkPoint();
        }
      
      decltype(auto)
      yield()  const
        {
          __throw_if_empty();
          return _rawCore().yield();
        }
      
      void
      iterNext()
        {
          __throw_if_empty();
          _rawCore().iterNext();
        }
    };
  
  
  
  
  template<typename T, class COR>
  class IterableDecorator
    : public COR
    {
      COR &      _core()       { return static_cast<COR&>       (*this); }
      COR const& _core() const { return static_cast<COR const&> (*this); }
      
    protected:
      void
      __throw_if_empty()  const
        {
          if (not isValid())
            _throwIterExhausted();
        }
      
    public:
      typedef T* pointer;
      typedef T& reference;
      typedef T  value_type;
      
      template<typename...ARGS>
      IterableDecorator (ARGS&& ...init)
        : COR(std::forward<ARGS>(init)...)
        { }
      
      IterableDecorator()                                     =default;
      IterableDecorator (IterableDecorator&&)                 =default;
      IterableDecorator (IterableDecorator const&)            =default;
      IterableDecorator& operator= (IterableDecorator&&)      =default;
      IterableDecorator& operator= (IterableDecorator const&) =default;
      
      
      /* === lumiera forward iterator concept === */
      
      explicit operator bool() const { return isValid(); }
      
      reference
      operator*() const
        {
          return _core().yield();      // core interface: yield
        }
      
      pointer
      operator->() const
        {
          return & _core().yield();    // core interface: yield
        }
      
      IterableDecorator&
      operator++()
        {
          _core().iterNext();          // core interface: iterNext
          return *this;
        }
      
      bool
      isValid ()  const
        {
          return _core().checkPoint(); // core interface: checkPoint
        }
      
      bool
      empty ()    const
        {
          return not isValid();
        }
      
      
      
      ENABLE_USE_IN_STD_RANGE_FOR_LOOPS (IterableDecorator);
      
      
      template<class T1, class T2>
      friend bool
      operator== (IterableDecorator<T1,COR> const& il, IterableDecorator<T2,COR> const& ir)
      {
        return (il.empty()   and ir.empty())
            or (il.isValid() and ir.isValid() and il._core() == ir._core());
      }
      
      template<class T1, class T2>
      friend bool
      operator!= (IterableDecorator<T1,COR> const& il, IterableDecorator<T2,COR> const& ir)
      {
        return not (il == ir);
      }
    };
  
  
  
  
  
  
  
  template<class IT>
  class RangeIter
    {
      IT p_;
      IT e_;
      
      using _ValTrait = meta::ValueTypeBinding<meta::remove_pointer_t<IT>>;
      
    public:
      using pointer    = typename _ValTrait::pointer;
      using reference  = typename _ValTrait::reference;
      
      using value_type = typename std::remove_reference<reference>::type;
      
      
      RangeIter (IT const& start, IT const& end)
        : p_(start)
        , e_(end)
        { }
      
      RangeIter ()
        : p_()
        , e_()
        { }
      
      
      template<class I2>
      RangeIter (I2 const& oIter)
        : p_(oIter.getPos())
        , e_(oIter.getEnd())
        { }
      
      explicit
      operator bool() const
        {
          return isValid();
        }
      
      
      /* === lumiera forward iterator concept === */
      
      reference
      operator*() const
        {
          _maybe_throw();
          return *p_;
        }
      
      pointer
      operator->() const
        {
          _maybe_throw();
          return &(*p_);
        }
      
      RangeIter&
      operator++()
        {
          _maybe_throw();
          ++p_;
          return *this;
        }
      
      bool
      isValid ()  const
        {
          return (p_!= IT()) && (p_ != e_);
        }
      
      bool
      empty ()    const
        {
          return not isValid();
        }
      
      
      const IT&  getPos()  const { return p_; }
      const IT&  getEnd()  const { return e_; }
      
      
      ENABLE_USE_IN_STD_RANGE_FOR_LOOPS (RangeIter);
      
      
    private:
      
      void
      _maybe_throw()  const
        {
          if (!isValid())
            _throwIterExhausted();
        }
    };
  
  
  
  template<class I1, class I2>
  inline bool operator== (RangeIter<I1> const& il, RangeIter<I2> const& ir)  { return (!il && !ir) || (il.getPos() == ir.getPos()); }
  
  template<class I1, class I2>
  inline bool operator!= (RangeIter<I1> const& il, RangeIter<I2> const& ir)  { return !(il == ir); }
  
  
  
  
  
  template<typename INT>
  class NumIter
    {
      INT i_;
      INT e_;
      
    public:
      typedef const INT* pointer;
      typedef const INT& reference;
      typedef       INT  value_type;
      
      NumIter (INT start, INT end)
        : i_(start)
        , e_(end)
        { }
      
      template<typename X>
      NumIter (X&& start, X&& end)
        : i_(std::forward<X>(start))
        , e_(std::forward<X>(end))
        { }
      
      NumIter ()
        : i_()
        , e_()
        { }
      
      // standard copy operations acceptable
      
      explicit
      operator bool() const
        {
          return isValid();
        }
      
      
      
      /* === lumiera forward iterator concept === */
      
      reference
      operator*() const
        {
          _maybe_throw();
          return i_;
        }
      
      pointer
      operator->() const
        {
          _maybe_throw();
          return &i_;
        }
      
      NumIter&
      operator++()
        {
          _maybe_throw();
          ++i_;
          return *this;
        }
      
      bool
      isValid ()  const
        {
          return (i_!= INT()) && (i_ < e_);   // NOTE: use comparison to detect iteration end
        }
      
      bool
      empty ()    const
        {
          return not isValid();
        }
      
      
      const INT&  getPos()  const { return i_; }
      const INT&  getEnd()  const { return e_; }
      
      
      ENABLE_USE_IN_STD_RANGE_FOR_LOOPS (NumIter);
      
      
    private:
      void
      _maybe_throw()  const
        {
          if (!isValid())
            _throwIterExhausted();
        }
    };
  
  
  
  template<class I1, class I2>
  inline bool operator== (NumIter<I1> const& il, NumIter<I2> const& ir)  { return (!il && !ir) || (il.getPos() == ir.getPos()); }
  
  template<class I1, class I2>
  inline bool operator!= (NumIter<I1> const& il, NumIter<I2> const& ir)  { return !(il == ir); }
  
  
  
  template<typename INT>
  inline NumIter<INT>
  eachNum (INT start, INT end)
  {
    return NumIter<INT> (start, end);
  }
  
  
  
  
  
  
  
  template<class TY>
  struct IterType;
  
  template<template<class,class> class Iter, class TY, class CON>
  struct IterType<Iter<TY,CON>>
    {
      typedef CON Container;
      typedef TY  ElemType;
      
      template<class T2>
      struct SimilarIter  
        {
          typedef Iter<T2,CON> Type;
        };
    };
  
  template<class IT>
  struct IterType<RangeIter<IT>>
    : IterType<IT>
    {
      template<class T2>
      struct SimilarIter  
        {
          typedef typename IterType<IT>::template SimilarIter<T2>::Type WrappedIter;
          typedef RangeIter<WrappedIter> Type;
        };
    };
  
  
  
  template<class IT>
  class ConstIter
    {
      IT i_;  
      
      
    public:
      typedef const typename IT::value_type value_type;
      typedef const typename IT::pointer    pointer;
      typedef const typename IT::reference  reference;
      
      ConstIter (IT srcIter)
        : i_(srcIter)
        { }
      
      explicit
      operator bool() const
        {
          return isValid();
        }
      
      
      
      /* === lumiera forward iterator concept === */
      
      reference
      operator*() const
        {
          return *i_;
        }
      
      pointer
      operator->() const
        {
          return i_.operator->();
        }
      
      ConstIter&
      operator++()
        {
          ++i_;
          return *this;
        }
      
      bool
      isValid ()  const
        {
          return bool(i_);
        }
      
      bool
      empty ()    const
        {
          return not isValid();
        }
      
      
      IT const&
      getBase()  const
        {
          return i_;
        }
      
      
      ENABLE_USE_IN_STD_RANGE_FOR_LOOPS (ConstIter);
    };
  
  
  template<class I1, class I2>
  inline bool operator== (ConstIter<I1> const& il, ConstIter<I2> const& ir)  { return il.getBase() == ir.getBase(); }
    
  template<class I1, class I2>
  inline bool operator!= (ConstIter<I1> const& il, ConstIter<I2> const& ir)  { return not (il == ir); }
  
  
  
}// namespace lib
#endif /*LIB_ITER_ADAPTER_H*/