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Groups > comp.lang.c++ > #84058
| From | Mr Flibble <flibble@reddwarf.jmc> |
|---|---|
| Newsgroups | comp.theory, comp.ai.philosophy, comp.lang.c, comp.lang.c++ |
| Subject | Re: Implementing a two-way Turing Machine tape as an improvement to std::deque |
| Message-ID | <20220513015816.00006f57@reddwarf.jmc> (permalink) |
| References | (4 earlier) <-s-dncjVifoXB-D_nZ2dnUU7_83NnZ2d@giganews.com> <20220513004049.00000d64@reddwarf.jmc> <HYudneQqVdKFAOD_nZ2dnUU7_83NnZ2d@giganews.com> <20220513005340.00001694@reddwarf.jmc> <Bo-dnemL1eT6P-D_nZ2dnUU7_81g4p2d@giganews.com> |
| Organization | Jupiter Mining Corp |
| Date | 2022-05-13 01:58 +0100 |
Cross-posted to 4 groups.
On Thu, 12 May 2022 19:12:22 -0500
olcott <NoOne@NoWhere.com> wrote:
> On 5/12/2022 6:53 PM, Mr Flibble wrote:
> > On Thu, 12 May 2022 18:49:43 -0500
> > olcott <NoOne@NoWhere.com> wrote:
> >
> >> On 5/12/2022 6:40 PM, Mr Flibble wrote:
> >>> On Thu, 12 May 2022 18:38:49 -0500
> >>> olcott <NoOne@NoWhere.com> wrote:
> >>>
> >>>> On 5/12/2022 6:22 PM, Mr Flibble wrote:
> >>>>> On Thu, 12 May 2022 18:09:39 -0500
> >>>>> olcott <NoOne@NoWhere.com> wrote:
> >>>>>
> >>>>>> On 5/12/2022 5:56 PM, Mr Flibble wrote:
> >>>>>>> On Thu, 12 May 2022 17:51:25 -0500
> >>>>>>> olcott <NoOne@NoWhere.com> wrote:
> >>>>>>>
> >>>>>>>> C/C++ people please critique this as the basis for an
> >>>>>>>> improvement to std::deque. It seems to have the key
> >>>>>>>> functionality of std::deque and does it much more simply
> >>>>>>>> while saving time and space.
> >>>>>>>> https://www.cplusplus.com/reference/deque/deque/
> >>>>>>>>
> >>>>>>>> #define tape_element unsigned char
> >>>>>>>>
> >>>>>>>> class Tape_Type
> >>>>>>>> {
> >>>>>>>> private:
> >>>>>>>> int Tape_Head = 0; // Can be negative
> >>>>>>>> std::vector<tape_element> Left; // Stores left
> >>>>>>>> expansion std::vector<tape_element> Right; // Stores right
> >>>>>>>> expansion tape_element & operator[](int index);
> >>>>>>>>
> >>>>>>>> public:
> >>>>>>>> void move_left(); // Tape_Head--;
> >>>>>>>> Left.push_back(0); as needed void move_right(); //
> >>>>>>>> Tape_Head++; Left.push_back(0); as needed void
> >>>>>>>> Write(tape_element Y){ this->operator[](Tape_Head) = Y; };
> >>>>>>>> tape_element Read() { return
> >>>>>>>> this->operator[](Tape_Head); }; Tape_Type(){
> >>>>>>>> Right.push_back('_'); } // constructor void Output(); };
> >>>>>>>>
> >>>>>>>> tape_element& Tape_Type::operator[](int index)
> >>>>>>>> {
> >>>>>>>> if (index > 0)
> >>>>>>>> return Right[index];
> >>>>>>>> int Left_Index = ((index * -1) -1);
> >>>>>>>> return Left[Left_Index];
> >>>>>>>> }
> >>>>>>>>
> >>>>>>>> void Tape_Type::Output()
> >>>>>>>> {
> >>>>>>>> printf("Tape_Type::Output()\n");
> >>>>>>>>
> >>>>>>>> if (Left.size())
> >>>>>>>> {
> >>>>>>>> int Last_One = Left.size() - 1;
> >>>>>>>> for (int N = Last_One; N >= 0; N--)
> >>>>>>>> {
> >>>>>>>> int TH = (N + 1) * -1; // determine Tape_Head
> >>>>>>>> from N printf("[%04d]:%c Left[%02d]\n", TH, Left[N], N);
> >>>>>>>> }
> >>>>>>>> }
> >>>>>>>> if (Right.size())
> >>>>>>>> for (int N = 0; N < Right.size(); N++)
> >>>>>>>> printf("[%04d]:%c Right[%02d]\n", N, Right[N],
> >>>>>>>> N); }
> >>>>>>>>
> >>>>>>>> void Tape_Type::move_left()
> >>>>>>>> {
> >>>>>>>> Tape_Head--;
> >>>>>>>> int Left_Index = ((Tape_Head * -1) -1);
> >>>>>>>> if (Left_Index == Left.size())
> >>>>>>>> Left.push_back('_');
> >>>>>>>> }
> >>>>>>>>
> >>>>>>>> void Tape_Type::move_right()
> >>>>>>>> {
> >>>>>>>> Tape_Head++;
> >>>>>>>> if (Tape_Head == Right.size())
> >>>>>>>> Right.push_back('_');
> >>>>>>>> }
> >>>>>>>
> >>>>>>> It might be a more appropriate solution than std::deque for
> >>>>>>> your specific use-case however it is NOT an improvement to
> >>>>>>> std::deque for the general case -- see my reply in the other
> >>>>>>> thread for why.
> >>>>>>>
> >>>>>>> /Flibble
> >>>>>>>
> >>>>>>
> >>>>>> I didn't see any reason why it would not make a better
> >>>>>> std::deque.
> >>>>>
> >>>>> Because it doesn't meet the complexity and referential integrity
> >>>>> requirements of std::deque.
> >>>>>
> >>>>> /Flibble
> >>>>>
> >>>>
> >>>> It is faster then std::deque.
> >>>> I couldn't find what you mean by referential integrity it has too
> >>>> many different meanings. invalidating iterators seemed to be what
> >>>> you mean otherwise I have no idea.
> >>>
> >>> I see you are choosing to ignore my reply in the other thread.
> >>> OK, I will repost why you are wrong here:
> >>>
> >>> * referential integrity and iterator invalidation are different
> >>> things: when you add or remove elements to either end of a
> >>> std::deque iterators are indeed invalidated however
> >>> references to existing elements remain valid
> >>
> >> Mine words the same way and has the added benefit of contiguous
> >> storage.
> >>
> >>> * If you do 1000 push_fronts followed by 1000 push_backs
> >>> followed by 1000 pop_fronts all is good however your next
> >>> pop_front will have linear complexity, O(n), as it will
> >>> necessitate removal of the first element of the right
> >>> std::vector.
> >>
> >> I don't think that this applies to the way that I implemented it.
> >> pop_front pops from the end of Left. pop_back pops from the end of
> >> Right. This is the key aspect that I used from David's two-stack
> >> approach.
> >
> > Then it is totally different to what std::deque offers: std::deque
> > allows ALL elements to be either popped from the front or back. Try
> > reading AND UNDERSTANDING what I wrote again.
> >
> > /Flibble
> >
>
> I could allow all elements to be popped from the front or the back
> too. Mine is much faster when you need far less than all elements.
What you have does not offer what std::deque offers so is not
equivalent to std::deque so can't be considered better than std::deque
for the general case (I don't care about your specific use-case).
/Flibble
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Implementing a two-way Turing Machine tape as an improvement to std::deque olcott <NoOne@NoWhere.com> - 2022-05-12 17:51 -0500
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Mr Flibble <flibble@reddwarf.jmc> - 2022-05-12 23:56 +0100
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque olcott <NoOne@NoWhere.com> - 2022-05-12 18:09 -0500
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Mr Flibble <flibble@reddwarf.jmc> - 2022-05-13 00:22 +0100
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque olcott <NoOne@NoWhere.com> - 2022-05-12 18:38 -0500
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Mr Flibble <flibble@reddwarf.jmc> - 2022-05-13 00:40 +0100
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque olcott <NoOne@NoWhere.com> - 2022-05-12 18:49 -0500
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Mr Flibble <flibble@reddwarf.jmc> - 2022-05-13 00:53 +0100
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque olcott <NoOne@NoWhere.com> - 2022-05-12 19:12 -0500
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Mr Flibble <flibble@reddwarf.jmc> - 2022-05-13 01:58 +0100
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque olcott <NoOne@NoWhere.com> - 2022-05-12 20:34 -0500
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Öö Tiib <ootiib@hot.ee> - 2022-05-12 21:05 -0700
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Mr Flibble <flibble@reddwarf.jmc> - 2022-05-13 08:02 +0100
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque tth <tth@none.invalid> - 2022-05-13 09:10 +0200
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque olcott <NoOne@NoWhere.com> - 2022-05-13 10:47 -0500
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Ben <ben.usenet@bsb.me.uk> - 2022-05-13 17:22 +0100
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Paavo Helde <eesnimi@osa.pri.ee> - 2022-05-13 19:31 +0300
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque olcott <NoOne@NoWhere.com> - 2022-05-13 10:58 -0500
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Mr Flibble <flibble@reddwarf.jmc> - 2022-05-13 17:02 +0100
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-05-13 12:44 -0700
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Richard Damon <Richard@Damon-Family.org> - 2022-05-12 19:23 -0400
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque olcott <NoOne@NoWhere.com> - 2022-05-12 18:32 -0500
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Ben <ben.usenet@bsb.me.uk> - 2022-05-13 01:06 +0100
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque olcott <NoOne@NoWhere.com> - 2022-05-12 19:55 -0500
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Mr Flibble <flibble@reddwarf.jmc> - 2022-05-13 02:01 +0100
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque olcott <NoOne@NoWhere.com> - 2022-05-12 20:36 -0500
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Mr Flibble <flibble@reddwarf.jmc> - 2022-05-13 08:04 +0100
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque olcott <NoOne@NoWhere.com> - 2022-05-13 11:00 -0500
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque Mr Flibble <flibble@reddwarf.jmc> - 2022-05-13 17:04 +0100
Re: Implementing a two-way Turing Machine tape as an improvement to std::deque olcott <NoOne@NoWhere.com> - 2022-05-13 12:05 -0500
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