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Date: Thu, 10 Dec 2015 12:03:30 +0800
Message-ID: <CADm_WcZdC-iNF=tMmYYafsaLaHUcck03zw8cdsSCCPvXdTNyrw@mail.gmail.com>
From: Jeff Garzik <jgarzik@gmail.com>
To: Luke Durback <luke.durback@gmail.com>
Content-Type: multipart/alternative; boundary=001a11343db82aa9190526834a94
Cc: Bitcoin development mailing list <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Standard BIP Draft: Turing Pseudo-Completeness
Precedence: list

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There is no need for a BIP draft.  "Turing complete" is just a fancy,
executive-impressing term for "it can run any computer program", or put
even more simply, "it can loop"

Furthermore, the specification of such a language is trivial.  It is the
economics of validation that is the complex piece.  Proving whether or not
a program will halt as expected - The Halting Problem - is near impossible
for most complex programs.  As a result, your proof is... running the
program.  That produces enormous validation consequences and costs for
generic-execution scripts when applied to a decentralized network of
validation P2P nodes.

If you need that capability, it is just as easy to use a normal C/C++/etc.
computer language, with your preferred algorithm libraries and development
tools.

See https://github.com/jgarzik/moxiebox for a working example of provable
execution.



On Thu, Dec 10, 2015 at 9:35 AM, Luke Durback via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> Hello Bitcoin-Dev,
>
> I hope this isn't out of line, but I joined the mailing list to try to
> start a discussion on adding opcodes to make Script Turing Pseudo-Complete
> as Wright suggested is possible.
>
> ---
>
> In line with Wright's suggestion, I propose adding a return stack
> alongside the, already existing, control stack.
>
> The principle opcodes (excluding conditional versions of call and
> return_from) needed are
>
> OP_DEFINITION_START FunctionName:  The code that follows is the definition
> of a new function to be named TransactionSenderAddress.FunctionName.  If
> this function name is already taken, the transaction is marked invalid.
> Within the transaction, the function can be called simply as FunctionName.
>
> OP_DEFINITION_END:  This ends a function definition
>
> OP_FUNCTION_NAME FunctionName:  Gives the current transaction the name
> FunctionName (this is necessary to build recursive functions)
>
> ---
>
> OP_CALL Namespace.FunctionName Value TransactionFee:  This marks the
> transaction as valid.  It also pushes the current execution location onto
> the return stack, debits the calling transaction by the TransactionFee and
> Value, and creates a new transaction specified by Namespace.FunctionName
> with both stacks continued from before (this may be dangerous, but I see no
> way around it) with the specified value.
>
> OP_RETURN_FROM_CALL_AND_CONTINUE:  This pops the top value off the return
> stack and continues from the specified location with both stacks in tact.
>
> ---
>
> It would also be useful if a transaction can create another transaction
> arbitrarily, so to prepare for that, I additionally propose
>
> OP_NAMESPACE:  Pushes the current namespace onto the control stack
>
> This, combined with the ability to make new transactions arbitrarily would
> allow a function to pay its creator.
>
>
>
> I understand that this isn't all that is needed, but I think it's a
> start.  I hope this proposal has met you all well,
>
> Luke Durback
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>

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<div dir=3D"ltr">There is no need for a BIP draft. =C2=A0&quot;Turing compl=
ete&quot; is just a fancy, executive-impressing term for &quot;it can run a=
ny computer program&quot;, or put even more simply, &quot;it can loop&quot;=
<div><br></div><div>Furthermore, the specification of such a language is tr=
ivial.=C2=A0 It is the economics of validation that is the complex piece.=
=C2=A0 Proving whether or not a program will halt as expected - The Halting=
 Problem - is near impossible for most complex programs.=C2=A0 As a result,=
 your proof is... running the program.=C2=A0 That produces enormous validat=
ion consequences and costs for generic-execution scripts when applied to a =
decentralized network of validation P2P nodes.</div><div><br></div><div>If =
you need that capability, it is just as easy to use a normal C/C++/etc. com=
puter language, with your preferred algorithm libraries and development too=
ls.</div><div><br></div><div>See=C2=A0<a href=3D"https://github.com/jgarzik=
/moxiebox">https://github.com/jgarzik/moxiebox</a> for a working example of=
 provable execution.</div><div><br></div><div><br></div></div><div class=3D=
"gmail_extra"><br><div class=3D"gmail_quote">On Thu, Dec 10, 2015 at 9:35 A=
M, Luke Durback via bitcoin-dev <span dir=3D"ltr">&lt;<a href=3D"mailto:bit=
coin-dev@lists.linuxfoundation.org" target=3D"_blank">bitcoin-dev@lists.lin=
uxfoundation.org</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote"=
 style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><d=
iv dir=3D"ltr"><div>Hello Bitcoin-Dev,<br></div><div><br></div><div>I hope =
this isn&#39;t out of line, but I joined the mailing list to try to start a=
 discussion on adding opcodes to make Script Turing Pseudo-Complete as Wrig=
ht suggested is possible.</div><div><br></div><div>---</div><div><br></div>=
<div>In line with Wright&#39;s suggestion, I propose adding a return stack =
alongside the, already existing, control stack.</div><div><br></div><div>Th=
e principle opcodes (excluding conditional versions of call and return_from=
) needed are</div><div><br></div><div>OP_DEFINITION_START FunctionName: =C2=
=A0The code that follows is the definition of a new function to be named Tr=
ansactionSenderAddress.FunctionName.=C2=A0 If this function name is already=
 taken, the transaction is marked invalid.=C2=A0 Within the transaction, th=
e function can be called simply as FunctionName.</div><div><br></div><div>O=
P_DEFINITION_END: =C2=A0This ends a function definition</div><div><div><br>=
</div><div>OP_FUNCTION_NAME FunctionName: =C2=A0Gives the current transacti=
on the name FunctionName (this is necessary to build recursive functions)</=
div></div><div><br></div><div>---</div><div><br></div><div>OP_CALL Namespac=
e.FunctionName Value TransactionFee: =C2=A0This marks the transaction as va=
lid.=C2=A0 It also pushes the current execution location onto the return st=
ack, debits the calling transaction by the TransactionFee and Value, and cr=
eates a new transaction specified by Namespace.FunctionName with both stack=
s continued from before (this may be dangerous, but I see no way around it)=
 with the specified value.</div><div><br></div><div>OP_RETURN_FROM_CALL_AND=
_CONTINUE: =C2=A0This pops the top value off the return stack and continues=
 from the specified location with both stacks in tact.</div><div><br></div>=
<div>---<br></div><div><br></div><div>It would also be useful if a transact=
ion can create another transaction arbitrarily, so to prepare for that, I a=
dditionally propose</div><div><br></div><div>OP_NAMESPACE: =C2=A0Pushes the=
 current namespace onto the control stack<br><br>This, combined with the ab=
ility to make new transactions arbitrarily would allow a function to pay it=
s creator.</div><div><br></div><div><br></div><div><br></div><div>I underst=
and that this isn&#39;t all that is needed, but I think it&#39;s a start.=
=C2=A0 I hope this proposal has met you all well,</div><div><br></div><div>=
Luke Durback</div></div>
<br>_______________________________________________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@lists.=
linuxfoundation.org</a><br>
<a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
rel=3D"noreferrer" target=3D"_blank">https://lists.linuxfoundation.org/mail=
man/listinfo/bitcoin-dev</a><br>
<br></blockquote></div><br></div>

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