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From: wij <wyniijj5@gmail.com>
Newsgroups: comp.theory
Subject: Re: How to write a self-referencial TM?
Date: Thu, 15 May 2025 09:38:48 +0800
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On Wed, 2025-05-14 at 17:19 -0700, Keith Thompson wrote:
> Andy Walker <anw@cuboid.co.uk> writes:
> > On 14/05/2025 21:16, Richard Heathfield wrote:
> > > On 14/05/2025 21:00, Keith Thompson wrote:
> > > > I presume that one-way and two-way infinite tapes are computational=
ly
> > > > equivalent, so the distinction doesn't matter all that much.
> >=20
> > 	Indeed, there are lots of computationally equivalent versions:
> >=20
> > =C2=A0-- two or more tapes [indeed, two-dimensional tapes]
> > =C2=A0-- one-way or two-way
> > =C2=A0-- "paper" tapes where you can punch holes to change the content =
but not
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 stick the chad back in to "unpunch" the =
holes
> > =C2=A0-- two symbol, three symbol, ...
> > =C2=A0-- move two or more spaces at a time
> > =C2=A0-- others I've forgotten
>=20
> Not to mention the very common variant where landing on Free Parking
> means you get all the money from the center of the board.=C2=A0 Or was th=
at
> something else?
>=20
> [...]

// Manpage of class Spu
NAME
       Spu - Class of general purpose Soft-CPU

SYNOPSIS
       Except POD types, C structures, all types are declared in namespace =
Wy.

       #include <CSCall/Sct.h>

       Spu  (Soft  CPU)  is  a revised model of Turing Machine and a class =
that
       acts like a general purpose CPU-based computing machine to  provide =
 se=E2=80=90
       mantics for computing language and for remote program communication.

       The  main differences of Spu and general purpose CPU (or TM) is that=
 Spu
       has no =C2=B4register=C2=B4 nor =C2=B4flag=C2=B4, Spu has only a tap=
e. The tape is initially
       empty. Every object (referred to as tape variable) in the tape is  a=
llo=E2=80=90
       cated via instruction Alloc and identified by a continuous index num=
ber.
       Tape variable can be any C++ type, including Spu.

       The  instruction  of Spu is application definable. Except necessary =
few,
       about  >30  instructions  are  defined  for  convenience,  see   man=
page
       Wy.Sct(3wy).

       Documentation following omits the scope name Wy::Sct for each occurr=
ence
       of Spu for clearity.

[cut]
----------------------

1. In Spu, objects in the tape are allocated (constructed).
2. Accessing the tape outside range will throw an error.
3. Instructions in Spu are class members. 'instructions' can be considered=
=20
   variable or stateful (useful in developing theory), because data structu=
re=C2=A0
   related to instruction is considered part of the instruction, simiar to =
the
   OO concept of C++ class.
4. Multi-tasking can be modeled by multi-instances of Spu (or tape variable
   can be an Spu object)