On Tue, Feb 15, 2022 at 10:45 PM Rusty Russell <ru...@rustcorp.com.au> wrote:
> Jeremy Rubin <jeremy.l.ru...@gmail.com> writes: > > Hi Rusty, > > > > Please see my post in the other email thread > > > https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2022-February/019886.html > > > > The differences in this regard are several, and worth understanding > beyond > > "you can iterate CTV". I'd note a few clear examples for showing that > "CTV > > is just as powerful" is not a valid claim: > > > > 1) CTV requires the contract to be fully enumerated and is non-recursive. > > For example, a simple contract that allows n participants to take an > action > > in any order requires factorially many pre-computations, not just linear > or > > constant. For reference, 24! is about 2**80. Whereas for a more > > interpretive covenant -- which is often introduced with the features for > > recursion -- you can compute the programs for these addresses in constant > > time. > > 2) CTV requires the contract to be fully enumerated: For example, a > simple > > contract one could write is "Output 0 script matches Output 1", and the > set > > of outcomes is again unbounded a-priori. With CTV you need to know the > set > > of pairs you'd like to be able to expand to a-priori > > 3) Combining 1 and 2, you could imagine recursing on an open-ended thing > > like creating many identical outputs over time but not constraining what > > those outputs are. E.g., Output 0 matches Input 0, Output 1 matches > Output > > 2. > > Oh agreed. It was distinction of "recursive" vs "not recursive" which > was less useful in this context. > > "limited to complete enumeration" is the more useful distinction: it's a > bright line between CTV and TXHASH IMHO. > If TXHASH is limited to requiring the flags be included in the hash (as is done with sighash) I believe TXHASH has the same "up front" nature that CTV has.
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