Date: Thu, 23 Dec 2021 12:55:31 +0100 (CET)
From: Prayank <prayank@tutanota.de>
To: Jeremy <jlrubin@mit.edu>
Message-ID: <Mrak4sc--7-2@tutanota.de>
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Cc: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] [Bitcoin Advent Calendar] Review of Smart
 Contract Concepts
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Hi Jeremy,

> This post covers some high-level smart contract concepts that different
opcodes or proposals could have (or not).
https://rubin.io/bitcoin/2021/12/04/advent-7/

Interesting post. I love the concept of recursion in programming. There is =
one Indian movie called 'Karthik calling Karthik' which is one of the ways =
I remember this concept.=20

> Recursive is pretty much just a fancy way of saying =E2=80=9Cloops=E2=80=
=9D. This is sometimesalso called =E2=80=9CTuring Complete=E2=80=9D.

Recently asked one dumb question on Stakexchange after reading a comment on=
 reddit, maybe you can add anything new in this:

https://bitcoin.stackexchange.com/questions/111337/loops-in-bitcoin-scripti=
ng

> Here, the contract terminates after one canceled request by moving the co=
inelsewhere.  It=E2=80=99s possible to emulate recursive behavior a limited=
 amount by=E2=80=9Cunrolling=E2=80=9D a loop.

I think this is what I did in the above link where for loop was replaced wi=
th if-else statements.

> However, unrolling has it=E2=80=99s limits. When choices(action A or B) a=
re introduced, unrolling can be less effective since you haveand exponentia=
l blowup (that means unrolling even like 32 steps might be toomany). Howeve=
r, there are some tricks that can be employed by a clever andcareful progra=
mmer to reduce this complexity through, for example, memoization.

Agree with limits and possibility of optimization.

> The key difference being that in the fully enumerated case we must know t=
he exact specifics of the contract and how it will execute, and in the open=
 ended contract case there are bits and pieces we can dynamically specify. =
If Alice is paid 1 BTC by December 25th, 2021 Midnight, then transfer 100 t=
okensto one of Bob=E2=80=99s Address B1, B2, or B3 at Bob=E2=80=99s discret=
ion.

Interesting

> Signing the transaction fee rate as a function of locktime

TIL


--=20
Prayank

A3B1 E430 2298 178F

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<div>Hi Jeremy,<br></div><div dir=3D"auto"><br></div><div dir=3D"auto">&gt;=
 This post covers some high-level smart contract concepts that different<br=
></div><div dir=3D"auto">opcodes or proposals could have (or not).<br></div=
><div dir=3D"auto">https://rubin.io/bitcoin/2021/12/04/advent-7/<br></div><=
div dir=3D"auto"><br></div><div dir=3D"auto">Interesting post. I love the c=
oncept of recursion in programming. There is one Indian movie called 'Karth=
ik calling Karthik' which is one of the ways I remember this concept. <br><=
/div><div dir=3D"auto"><br></div><div dir=3D"auto">&gt; Recursive is pretty=
 much just a fancy way of saying =E2=80=9Cloops=E2=80=9D. This is sometimes
also called =E2=80=9CTuring Complete=E2=80=9D.<br></div><div dir=3D"auto"><=
br></div><div dir=3D"auto">Recently asked one dumb question on Stakexchange=
 after reading a comment on reddit, maybe you can add anything new in this:=
<br></div><div dir=3D"auto"><br></div><div dir=3D"auto">https://bitcoin.sta=
ckexchange.com/questions/111337/loops-in-bitcoin-scripting<br></div><div di=
r=3D"auto"><br></div><div dir=3D"auto">&gt; Here, the contract terminates a=
fter one canceled request by moving the coin
elsewhere.  It=E2=80=99s possible to emulate recursive behavior a limited a=
mount by
=E2=80=9Cunrolling=E2=80=9D a loop.<br></div><div dir=3D"auto"><br></div><d=
iv dir=3D"auto">I think this is what I did in the above link where for loop=
 was replaced with if-else statements.<br></div><div dir=3D"auto"><br></div=
><div dir=3D"auto">&gt; However, unrolling has it=E2=80=99s limits. When ch=
oices
(action A or B) are introduced, unrolling can be less effective since you h=
ave
and exponential blowup (that means unrolling even like 32 steps might be to=
o
many). However, there are some tricks that can be employed by a clever and
careful programmer to reduce this complexity through, for example, memoizat=
ion.<br></div><div dir=3D"auto"><br></div><div dir=3D"auto">Agree with limi=
ts and possibility of optimization.<br></div><div dir=3D"auto"><br></div><d=
iv dir=3D"auto">&gt; The key difference being that in the fully enumerated =
case we must know the exact specifics of the contract and how it will execu=
te, and in the open ended contract case there are bits and pieces we can dy=
namically specify. If Alice is paid 1 BTC by December 25th, 2021 Midnight, =
then transfer 100 tokens
to one of Bob=E2=80=99s Address B1, B2, or B3 at Bob=E2=80=99s discretion.<=
br></div><div dir=3D"auto"><br></div><div dir=3D"auto">Interesting<br></div=
><div dir=3D"auto"><br></div><div dir=3D"auto"><div>&gt; Signing the transa=
ction fee rate as a function of locktime<br></div><div><br></div><div>TIL<b=
r></div></div><div dir=3D"auto"><br></div><div><br></div><div>-- <br></div>=
<div>Prayank<br></div><div><br></div><div dir=3D"auto">A3B1 E430 2298 178F<=
br></div>  </body>
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